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Engineering Geological Assessment and Rock Mass
Engineering Geological Assessment and Rock Mass
Characterization of the Asmari Formation (Zagros Range)
as Large Dam Foundation Rocks
in Southwestern Iran
By
Mehran Koleini
Department of Geology
UNIVERSITY OF PRETORIA
South Africa
Supervisor:
Co-supervisor:
Prof. Jan Louis Van Rooy
Prof. Adam Bumby
Submitted in partial fulfillment of the requirement for the degree of Doctor of Philosophy
(Ph.D.) in Engineering Geology in the Faculty of Natural and Agricultural Sciences,
University of Pretoria
Pretoria
2012
© University of Pretoria
In the Name of God
I, Mehran Koleini hereby declare that this thesis,
“Engineering Geological Assessment and Rock Mass Characterization of the Asmari
Formation (Zagros Range) as Large Dam Foundation Rocks in Southwestern Iran”
which I hereby submit for the degree PhD. (Engineering Geology) at the University of
Pretoria, is my own work and has not been submitted by me for a degree at this or any other
tertiary institution.
2012
Acknowledgements
The following people were of great help and guidance during this research:

First, I would like to express my special thanks to my supervisor, Prof. J. L. Van Rooy
for offering me the opportunity to carry out my research, for his full support and
valuable guidance.

I particularly thank Prof. A. Bumby as my Co-supervisor for his very useful
discussions in this research.

I am very grateful to Prof. P.G. Eriksson as Head of Department of Geology for his
administrative guidances.

I want to express my gratitude to,
Dr. M. Hashemi (Dept. of Civil Engineering, University of Isfahan-Iran)
for his helpful consultations during my research in Iran.

I would also like to thank
Eng. Banihashemi as Head of Geotechnical office of Mahab Ghodss Consulting
Engineers Company, Ministry of Energy- Iran, who provided me with research
facilities at Tehran central office, in addition to my field works in Iran.
i
Abstract:
The Zagros fold-thrust belt results from the continent-continent collision between the
Arabian margin and the Eurasian plate following the closure of the Neo-Tethys Ocean during
the Tertiary. Despite some ongoing controversies about the timing of the onset of the collision
there is little doubt that the main episode of the cover shortening in the Zagros folded belt
occurred since about 10 Ma as suggested by the youngest folded strata of the Agha Jari red
marls.
Shortening by about 70 km derived from balanced sections across the Zagros folded belt,
yields shortening rates of 7 km Ma-1 consistent with the present-day rates of 0.7 cm yr-1 based
on GPS studies. A major unconformity between the Agha Jari formation and the Bakhtyari
conglomerates indicates that cover shortening decreased or ceased 5 Ma ago. During or since
the deposition of the Bakhtyari Formation, the Zagros fold belt underwent a regional uplift
whose origin still remains enigmatic. The deformation is characterized by periodic folding
with axial lengths sometimes greater than 200 km. This fold geometry is outlined by the
limestone beds of the Asmari Formation, which is one of the main oil reservoirs in the Zagros.
The Zagros also serves as the main originating headspring of the rivers running into the
Persian Gulf and Oman Sea watersheds. Among all these rivers, the major ones are: Arvand
Rud, Gamasb, Karun, Rajah, Zaal and Marun join and form Jarahi, Seymareh, Qareh
Aqhaj, Zohreh, Dalaki, Mend, Shur, Minab, Mehran and Naband. Therefore, the Zagros
region has high potential for dam construction to control surface water for electric energy,
water supply for irrigation of agricultural lands and land reclamation.
Among various formations in the Zagros region, the Asmari Formation limestone with
relatively exclusive characteristics such as rigidity and morphology is a suitable rock
foundation for dams in the Zagros range. It should be considered that the Asmari limestones
constitute a series of double plunging, asymmetrical folds with northwest-southeast trend
and that the southern flanks are steeper than the north-eastern ones (70° to 90º, locally
reversed). Due to varying inclinations, there are much more curvatures of strata in the
southwestern flanks of folded structures, with different characteristics of the rock mass in the
two flanks of the anticlines. The anticlines, particularly in the Asmari Formation, contain
tension-induced, open fracturing which has introduced significant secondary permeability.
Engineering geological investigations indicate that there is a clear relationship between rock
mass characteristics of the Asmari Formation and tectonic activities such as various tilting
and curvature rates of strata at folded structures in the Zagros Mountain range.
In this regard it should be considered that the upper and middle units of the Asmari Formation
that constituted the main dam foundation rock mass on the northern flanks are influenced by
karstification processes which have resulted from aggressive mineral waters. Thus huge karst
features and cavities can be observed, where the Gachsaran evaporites stratigraphically
overlie Asmari Formation succession limestones. The aggressive mineral waters originating
from the Gachsaran Formation play the main role in karstification of the Asmari Formation
limestones, whereas the lower Asmari is less influenced by these solutions and karstification
processes as it is restricted to where the Karun-3 and Karun-4 dams are situated.
Reassessment of available data and geological investigations during this research, lead to a
new proposed configuration of engineering characterization of the rock mass for the Asmari
formation limestones in the Zagros Region.
ii
TABLE OF CONTENTS
ACKNOWLEDGEMENTS ..................................................................................................................................... I
ABSTRACT: .......................................................................................................................................................... II
TABLE OF CONTENTS ...................................................................................................................................... III
LIST OF FIGURES ..............................................................................................................................................VII
LIST OF TABLES .............................................................................................................................................. XV
CHAPTER 1
INTRODUCTION
1.1. INTRODUCTION ........................................................................................................................................... 1
1.1.1. Aims of Thesis ................................................................................................................................ 4
1.1.2. Previous Work
............................................................................................................................... 5
1.2. GEOGRAPHY OF IRAN
.............................................................................................................................. 5
1.2.1. Topography
................................................................................................................................... 6
1.2.2. Climate and Water Resources
...................................................................................................... 7
1.3. GEOLOGY OF IRAN
.................................................................................................................................. 8
1.3.1. Structural Units
............................................................................................................................. 8
1.3.1.1. Zagros
................................................................................................................................... 8
1.3.1.2. Zagros Thrust Zone
................................................................................................................ 9
1.3.1.3. Sanandaj – Sirjan Metamorphic Belt (SS) ................................................................................. 9
1.3.1.4. Urumiyeh–Bazman Volcanic Belt (UB) ................................................................................... 10
1.3.1.5. Central –East Iran Micro Plate .............................................................................................. 10
1.3.1.6. Makran and Zabol –Baluch Zone, Southeast Iran .................................................................... 10
1.3.1.7. Alborz
................................................................................................................................. 10
1.3.1.8. Kopet-Dagh
......................................................................................................................... 10
1.3.2. Stratigraphy of Iran
..................................................................................................................... 10
1.3.2.1. Precambrian Basement
......................................................................................................... 10
1.3.2.2. Palaeozoic Platform
............................................................................................................. 11
1.3.2.2.1. Precambrian–Cambrian Boundary
................................................................................ 11
1.3.2.2.2. Infracambrian –Ordovician
.......................................................................................... 11
1.3.2.2.3. Silurian to Lower Devonian
......................................................................................... 11
1.3.2.2.4. Middle Devonian to Carboniferous ............................................................................... 12
1.3.2.2.4.1. Alborz
.............................................................................................................. 12
1.3.2.2.4.2. Central Iran
...................................................................................................... 12
1.3.2.2.4.3. Zagros Area
...................................................................................................... 12
1.3.2.2.5. Permian Sedimentary Cycle
......................................................................................... 12
1.3.2.2.6. Permian –Triassic Boundary
........................................................................................ 13
1.3.2.3.Mesozoic
............................................................................................................................. 13
1.3.2.3.1. Lower and Middle Triassic Sedimentary Cycle ................................................................. 13
1.3.2.3.2. Upper Triassic to Middle Jurassic Sedimentary Cycle ....................................................... 13
1.3.2.3.3. Middle and Upper Cretaceous
...................................................................................... 14
1.3.2.4. Tertiary
............................................................................................................................... 15
1.3.2.4.1. Palaeogene (excluding Upper Oligocene) ...................................................................... 15
1.3.2.4.2. Upper Oligocene to Lower Miocene
............................................................................. 15
1.3.2.4.3. Neogene Basin .................................................................................................................... 16
1.3.2.4.3.1. Central Iran ............................................................................................................. 16
1.3.2.4.3.2. Lut Basin
.......................................................................................................... 17
1.3.2.4.3.3. Makran and Baluchistan (Southeast Iran)
............................................................ 17
1.3.2.4.3.4. Zagros
.............................................................................................................. 17
1.4. ZAGROS STRUCTURE .................................................................................................................................. 19
1.5. SEISMICITY IN THE ZAGROS FOLDED BELT
........................................................................................... 20
CHAPTER 2
THE GEOLOGY OF THE ASMARI FORMATION AND ASSOCIATED UNITS
2.1. SEQUENCE STRATIGRAPHY OF THE ZAGROS FOLD-THRUST BELT
iii
......................................................... 21
2.1.1. Tectonic Setting
........................................................................................................................... 21
2.1.2. Stratigraphy
................................................................................................................................ 23
2.1.2.1. Lithostratigraphic Units of the Zagros Fold-Thrust Belt ........................................................... 23
2.1.2.1.1. Neoproterozoic to Devonian (?) Pull-apart Basin and Epicontinental Platform Deposits .. 23
2.1.2.1.2. Permian to Triassic Epi-Pangean Platform Deposits ...................................................... 23
2.1.2.1.3. Jurassic to Upper Cretaceous Continental-Shelf Deposits ................................................ 25
2.1.2.1.4. Upper Cretaceous to Recent Proforeland Basin Deposits ................................................. 25
2.2. STRATIGRAPHIC UNITS OF THE ASMARI FORMATION ............................................................................ 30
2.2.1. Lithostratigraphic Units
.............................................................................................................. 30
2.2.2. Biostratigraphic Units of the Asmari Formation
......................................................................... 35
CHAPTER 3
ROCK MASS DESCRIPTION
3.1. INTRODUCTION ......................................................................................................................................... 36
3.2. ENGINEERING ROCK MASS CLASSIFICATION
........................................................................................ 37
3.2.1. Rock Quality Designation (RQD) ................................................................................................. 37
3.2.1.1. Disadvantages of RQD .......................................................................................................... 38
3.2.2.Rock Mass Rating (RMR)
............................................................................................................. 38
2.1.3. Rock Tunneling Quality Index, Q ................................................................................................. 41
2.1.4. Geological Strength Index (GSI)
.................................................................................................. 47
3.2.4.1. When not to Use GSI ............................................................................................................. 48
3.2.4.2. Projection of GSI values into the Ground ................................................................................ 49
3.2.5. Slope Stability
.............................................................................................................................. 50
3.2.5.1. Slope Mass Rating (SMR) ...................................................................................................... 50
3.2.5.2. Falling Rock Hazard Index (FRHI) ........................................................................................ 52
3.3. Using Rock Mass Classification Systems
................................................................................. 54
CHAPTER 4
GEOLOGY OF THE PROJECT SITES
4.1. INTRODUCTION ...................................................................................................................................... 55
4.2. GEOLOGY OF THE KARUN-3 DAM AND POWER PLANT
.......................................................................... 57
4.2.1. Objectives and benefits of the project
........................................................................................ 57
4.2.2. Bedrock Geology of Project Area
................................................................................................ 58
4.2.3. Structural Geology
...................................................................................................................... 61
4.2.3.1. Joint Study
........................................................................................................................... 63
4.2.3.1.1. Direction of Principal Stresses at Karun-3 Damsite .......................................................... 63
4.2.3.2. Regional Faults
.................................................................................................................... 67
4.2.3.3. Local Faults
......................................................................................................................... 67
4.3. GEOLOGY OF THE KARUN-4 DAM AND POWER PLANT
.......................................................................... 69
4.3.1. Objective and benefits of the project
.......................................................................................... 70
4.3.2. Bedrock Geology of Project Area
................................................................................................ 70
4.3.3. Hydrogeological Characteristic of the Dam Location
.................................................................. 73
4.3.3.1. Karst Features, Porosity and Permeability .............................................................................. 73
4.3.3.2. Watertightness of Reservoir ................................................................................................... 73
4.3.4. Structural Geology
...................................................................................................................... 75
4.3.4.1. Regional Faults
.................................................................................................................... 75
4.3.4.2. Local Faults
......................................................................................................................... 76
4.3.4.3. Joint Study
........................................................................................................................... 80
4.4. GEOLOGY OF THE MARUN DAM AND POWER PLANT ............................................................................. 83
4.4.1. Objectives and benefits of the project
........................................................................................ 84
4.4.2. Bedrock Geology of Project Area
................................................................................................ 84
4.4.3. Hydrogeological Characteristic of the Dam Location
.................................................................. 86
4.4.3.1. Karst Features, Porosity and Permeability .............................................................................. 86
4.4.4. Tectonic Setting
........................................................................................................................... 89
4.4.4.1. Joint Study
........................................................................................................................... 91
4.5. GEOLOGY OF THE SEYMAREH DAM AND POWER PLANT ........................................................................ 94
1.5.4. Objective and benefits of the project
............................................................................... 95
4.5.2. Bedrock Geology of Project Area
................................................................................................ 96
4.5.3.Hydrogeological Characteristics of the Dam Location
................................................................ 99
iv
4.5.3.1. Karst Features, Porosity and Permeability .............................................................................. 99
4.5.4. Tectonic Setting
......................................................................................................................... 102
4.5.4.1. Regional Tectonic
............................................................................................................. 102
4.5.4.2. Small Scale Faults and Direction of Principal Stresses at the Seymareh Dam site .................. 103
4.5.4.3. Joint Study
......................................................................................................................... 106
4.6. GEOLOGY OF THE SALMAN FARSI DAM AND POWER PLANT
............................................................... 109
1.6.4. Objective and benefits of the project
............................................................................. 109
4.6.2. Bedrock Geology of Project Area
.............................................................................................. 110
4.6.3. Hydrogeological Characteristic of the Dam Location
................................................................ 113
4.6.3.1. Karst Features and Porosity
................................................................................................ 113
4.6.3.2. Speleological Reconnaissance ............................................................................................. 115
4.6.3.3. Permeability at the Dam site ................................................................................................ 116
4.6.3.4. Reservoir Watertightness ..................................................................................................... 118
4.6.4.Tectonic Setting
......................................................................................................................... 119
4.6.4.1. Regional Tectonic ............................................................................................................... 119
4.6.4.2. Large Scale Structures in the Project Area ............................................................................ 121
4.6.4.3. Joint Study and Direction of Principal Stresses at the Salman Farsi Dam site ......................... 122
4.7.PETROGRAPHICAL ANALYSIS OF THE ASMARI FORMATION AT FIVE DAM SITES
................................. 126
4.7.1. Standard Facies Zones and the Wilson Model
.......................................................................... 129
4.8. HYDROGEOLOGY ................................................................................................................................. 130
4.8.1. Weathering and Karst Features
................................................................................................ 130
CHAPTER 5
THE ENGINEERING GEOLOGICAL CHARACTERISTICS OF THE ASMARI
FORMATION ROCK MASS AT THE CONSTRUCTION SITES OF FIVE LARGE DAMS
5.1. INTRODUCTION .................................................................................................................................... 137
5.2. ENGINEERING GEOLOGICAL CHARACTERISTICS OF THE KARUN-3 DAM AND POWER PLANT
(ENGINEERING ROCK MASS CLASSIFICATION OF THE ASMARI FORMATION) ............................................ 138
5.2.1. Diversion Tunnel
........................................................................................................................ 138
5.2.1.1. Lower Unit- As.1 (Lower Asmari Formation- 4a1, 4a2, 4a3) .................................................. 138
5.2.2. Hydropower Tunnels
................................................................................................................. 145
5.2.2.1. Lower Asmari (4a1, 4a2, 4a3, 4a4) ...................................................................................... 145
5.2.2.2. Unit- As.2 (Upper Asmari Formation- 4b) ............................................................................. 148
5.2.3. Hydrogeology of Project Site
..................................................................................................... 153
5.2.3.1. Hydraulic Conductivity ....................................................................................................... 153
5.2.3.2. Curtain Grouting
................................................................................................................ 154
5.2.4. Watertightness of Reservoir
...................................................................................................... 154
5.3. ENGINEERING GEOLOGICAL CHARACTERISTICS OF THE KARUN-4 DAM AND POWER PLANT
(ENGINEERING ROCK MASS CLASSIFICATION OF THE ASMARI FORMATION) ............................................ 156
5.3.1. Diversion Tunnel
........................................................................................................................ 156
5.3.1.1. Lower Unit (Lower Asmari Formation- As.1) ........................................................................ 156
5.3.1.2. Middle Unit (Middle Asmari Formation- As.2) ...................................................................... 161
5.3.1.3. Upper Unit (Upper Asmari Formation- As.3) ........................................................................ 163
5.4. ENGINEERING GEOLOGICAL CHARACTERISTICS OF THE MARUN DAM AND POWER PLANT ................. 167
(ENGINEERING ROCK MASS CLASSIFICATION OF THE ASMARI FORMATION) ............................................ 167
5.4.1. Diversion Tunnels
...................................................................................................................... 167
5.4.1.1. Lower Unit (Lower Asmari Formation- As.1) ........................................................................ 167
5.4.1.2. Middle Unit (Middle Asmari Formation- As.2) ...................................................................... 172
5.4.1.3. Upper Unit (Upper Asmari Formation- As.3) ......................................................................... 173
5.5. ENGINEERING GEOLOGICAL CHARACTERISTICS OF THE SEYMAREH DAM AND POWER PLANT PROJECT
(ENGINEERING ROCK MASS CLASSIFICATION OF THE ASMARI FORMATION) ............................................ 178
5.5.1. Lower Unite (Lower Asmari Formation- As.1) ........................................................................... 178
5.5.2. Middle Unit (Middle Asmari Formation- As.2) .......................................................................... 180
5.5.3. Upper Unit (Upper Asmari Formation- As.3) ............................................................................. 183
5.6. ENGINEERING GEOLOGICAL CHARACTERISTICS OF THE SALMAN FARSI DAM AND POWER PLANT PROJECT
(ENGINEERING ROCK MASS CLASSIFICATION OF THE ASMARI FORMATION)……………………………191
5.6.1. Middle Unit (Middle Asmari Formation- As.2) .......................................................................... 191
5.6.2. Lower Unit (Lower Asmari Formation- As.1) ............................................................................. 197
5.6.3. Upper Unite (Upper Asmari Formation- As.3) ........................................................................... 199
v
CHAPTER 6
THE ENGINEERING GEOLOGY OF THE ASMARI FORMATION AND IMPLICATIONS
ON THE FIVE DAM SITES
6.1. INTRODUCTION .................................................................................................................................... 203
6.2. PERMEABILITY AND WATERTIGHTNESS
.............................................................................................. 205
6.3. SLOPE STABILITY ANALYSIS
............................................................................................................... 208
6.3.1. Slope Mass Rating (SMR) .......................................................................................................... 208
6.3.2. Falling Rock Hazard Index (FRHI) .............................................................................................. 210
6.3.3. Rock Slope Stabilization
............................................................................................................ 214
6.4. EFFECT OF RESERVOIR IMPOUNDING ................................................................................................... 218
6.5. ENGINEERING CLASSIFICATION OF ROCK MASS .................................................................................. 218
6.6. STABILITY OF DAMS AGAINST HORIZONTAL SLIDING
......................................................................... 224
6.6.1. DMR (Dam Mass Rating) ........................................................................................................... 224
6.7. UNDERGROUND ROCK SUPPORT
......................................................................................................... 225
6.8. CUTTABILITY OF ASMARI FORMATION LIMESTONE
............................................................................ 226
6.9. NET ALLOWABLE BEARING PRESSURE CLASSIFICATION ..................................................................... 227
6.10. FOUNDATION CONSIDERATION ............................................................................................................ 229
6.10.1. Grouting .................................................................................................................................... 229
6.10.1.1. Consolidation Grouting ....................................................................................................... 229
6.10.1.2. Curtain Grouting ................................................................................................................ 229
6.10.2. Treatment of Large Caverns ...................................................................................................... 230
6.11. CONSTRUCTION MATERIALS ............................................................................................................... 230
6.11.1. Granular Materials .................................................................................................................... 230
6.11.2. Excavated Rocks ........................................................................................................................ 230
6.11.3. Impervious Fill ........................................................................................................................... 231
6.12. RESERVOIR-INDUCED EARTHQUAKES ................................................................................................. 231
6.13. CONCLUSION AND RECOMMENDATIONS .............................................................................................. 232
LIST OF REFERENCES: ................................................................................................................................... 236
APPENDIX 1 ...................................................................................................................................................... 244
Petrographic Description of the Various Units of the Asmari Formation in Karun-3 Dam .................. 244
APPENDIX 2 ...................................................................................................................................................... 245
Petrographic Description of the Various Units of the Asmari Formation in Karun-4 Dam .................. 245
APPENDIX 3 ...................................................................................................................................................... 246
Petrographic Description of the Various Units of the Asmari Formation in Marun Dam ..................... 246
APPENDIX 4 ...................................................................................................................................................... 247
Petrographic Description of the Various Units of Asmari Formation in Seymareh Dam ..................... 247
APPENDIX 5 ...................................................................................................................................................... 248
Petrographic Description of the Various Units of Asmari Formation in Salman Farsi Dam……….…248
vi
List of figures
Figure 1.1. The map indicates some major rivers in Iran and dam localities in the Zagros region (research area).
Salman Farsi dam (Sa), Marun dam (M), Karun-4 dam (K4), Karun-3 dam (K3), Seymareh dam (Se). ................ 4
Figure 1.2. The topographic map of Iran (Iran topo en.jpg, 2006). ........................................................................ 6
Figure 1.3. The main structural units of Iran (after Berberian and King, 1961). .................................................... 9
Figure 1.4. Geological map of Iran, SSZ represent the Sanandaj-Sirjan Zone (after Pollastro et al., 1997). The
dam localities in Zagros region are presented by red triangle. .............................................................................. 14
Figure 1.5. Stratigraphic nomenclature of rock units and age relationships in the Zagros basin (after Rezaie and
Nogole-Sadat, 2004). ............................................................................................................................................. 18
Figure 1.6. A generalized cross-section through the Zagros Mountains. Note the location of the MZRF or Main
Zagros Thrust (MZT) and the folding within the Zagros fold Belt (ZFB) Sediment ages are labeled as follows;
Neogene (N), Palaeogene (Pg), and Palaeozoic (P). Also shown are radiolarites near suture zone(R), the
Sanandaj-Sirjan Zone (SSZ), and the Urumiyeh Dokhtar volcanic zone (UDVZ) (after Stocklin, 1968)............. 19
Figure 1.7. An oblique satellite image of the Zagros Mountain range (Earthobservatory.nasa.gov., 1992). ........ 19
Figure 1.8. Seismicity map of Iran. It shows the high inhomogeneity and seismic activity dispersion of the
Iranian Plateau (after International Institute of Earthquake Engineering and Seismology-IIEES, 2004).............. 20
Figure 2.1. The Zagros orogenic belt and its subdivisions. Abbreviations; EAF – East Anatolian fault; OLOman line; UDMA – Urumieh-Dokhtar magmatic arc; ZDF – Zagros deformational front; ZFTB – Zagros foldthrust belt; ZIZ – Zagros imbricate zone: ZS – Zagros suture; Red dots show location of the stratigraphic
columns. Hydrocarbon fields of the region (oil in green and gas in pink) are also shown (after Alavi, 2004). .... 22
Figure 2.2. Stratigraphy column of the Zagros fold-thrust belt of Iran. (after Alavi, 2003). ................................ 24
Figure 2.3. A, B, C, D. Four stratigraphic correlation profiles across the Zagros fold-thrust belt of Iran. See
Figure 2.1 for locations of the stratigraphic profiles. Three megasequences (IX, X, and XI of Figure2.2) of the
proforeland basin are distinguished. The stratigraphic columns restored to their pre -Zagros-deformation
positions. The latest Turonian regional unconformity is chosen as the datum. Non-Iranian stratigraphic
nomenclatures are shown in black (after Alavi, 2004). ....................................................................................... 26
Figure 2.4. Correlation chart of the tertiary of southwest Iran. (after Vaziri et al., 2006, adopted from Ala, 1982).
The line indicates the correlation direction and the triangles show locality of some geological columns that are
described in Figure 2.5 to Figure 2.8. .................................................................................................................... 32
Figure 2.5. Stratigraphic column of Ahwaz Sandstone member in oil well No. 1, Ab Teymoor Oil field
(supplementary section (left- 1968) and oil well No.6, In Ahwaz Oil field (right- 1965), (after Motiei, 1993).33
Figure 2.6. Stratigraphic column of Kalhur evaporite member/ Supplementary section, Changoleh, well No.1
(after Motiei, 1993). .............................................................................................................................................. 34
Figure 2.7. Lithostratigraphic columns of the Asmari Formation in the Khaviz section, Khuzestan Province (afer
Vazirimoghdam et al., 2005). ................................................................................................................................ 34
Figure 2.8. Lithostratigraphic columns of the Asmari Formation in Lali and Kuhe Asmari sections – Khuzestan
Province (after Vazirimoghadam et al., 2005). ...................................................................................................... 35
Figure 3.1. Relationship between Stand-up time, span and RMR classification (after Bieniawski (1989). ......... 41
Figure 3.2. Estimated support categories based on the tunnelling quality index Q (after Grimstad and Barton,
1993)...................................................................................................................................................................... 47
Figure 3.3. The General Geological Strength Index (GSI) chart for jointed rock masses estimates from the
geological observations (after Hoek and Brown 1997, Hoek and Karzulovic, 2000). .......................................... 50
Figure 4.1. The topographical map of Zagros folded belt and locations of five dam sites. Seymareh (4), Karun-3
(1), Karun-4 (2), Marun (3) and Salman Farsi (5). The direction of shortening at the region due to tectonic
movements are indicated by white arrows. (Lexicorient base map, 2001). ........................................................... 55
Figure 4.2.1. The satellite image of Karun-3 dam project and surrounding area before reservoir impoundment.
This project located at 28 km east of Izeh town in Khuzestan Province. Access road of Dehdez – Izeh can be
seen on middle part of picture (Google Earth, European Technology, 2009). ...................................................... 57
Figure 4.2.2. Karun-3 dam a double curvature concrete arch dam constructed on the Karun River. ................... 58
Figure 4.2.3. Geological map of the Karun-3 Dam and power plant site (after MG co., 2009). .......................... 59
Figure 4.2.4. Lithological column of the Asmari Formation in the Karun-3 dam site.......................................... 60
Figure 4.2.5. Geological section along Karun-3 Dam axes. The hydropower tunnels (4 circular 15 m, 10 m in
dia.) and the diversion tunnel (15 m in diameter) located on right abutment (after MG co., 2009). ..................... 61
Figure 4.2.6. The major seismically active faults in the study area at the Zagros region. (after International
Institute of Earthquake Engineering and Seismology- Iran, 2003)........................................................................ 62
Figure 4.2.7. The direction of 1 / Shortening at Karun-3 dam site. .................................................................... 63
Figure 4.2.8. The Stereographic projection of joints at the right flank, A- Contour plot, B- Rosette plot, and CPole plot of joints (Dips©, equal area projection-Schmidt net, lower hemisphere). ............................................. 64
vii
Figure 4.2.9. The Stereographic projection of joints at the left flank. A- Contour plot, B- Rosette plot, and CPole plot of joints (Dips©, equal area projection-Schmidt net, lower hemisphere). ............................................. 65
Figure 4.2.10. The Stereographic projection of bedding planes at the Karun-3 dam and identification of principal
stresses that have impressed on dam site. The direction of 1 is coincident with direction of shortening in the
Zagros Folded belt (Dips©, equal area projection-Schmidt net, lower hemisphere). ............................................ 66
Figure 4.2.11. Karun-3 Dam and Power plant. The subunits of the Asmari Formation can be seen in both
abutments. The Doshablori Fault strikes in a northwest-southeast direction and passes within 500 m southwest of
the dam site. ........................................................................................................................................................... 68
Figure 4.3.1. The satellite image of Karun-4 dam and power plant project on the Karun River. The dam site
located on the southern flank of the Kuh Sefid Anticline and the foundation rocks is Asmari Formation limestone
related to Oligomiocene in age. The various parts of the project can be observed as well (Google Earth,
European Technology, 2009). ............................................................................................................................... 69
Figure 4.3.2. The Karun-4 dam site constructed at the southern flank of the Kuh Sefid Anticline (2006). ......... 70
Figure 4.3.3. Geological map of the Karun-4 dam and power plant project in the Zagros Range of Iran. (after
MG. co., 1989). ..................................................................................................................................................... 71
Figure 4.3.4. Lithological column of the Asmari Formation at the Karun-4 dam site. ......................................... 72
Figure 4.3.5. Some karstic features formed due to dissolution of limestone along discontinuity surfaces. The
discontinuity surfaces mainly constituted by compressional tectonic movements at the region and then enlarged
by water dissolution. The small fibrous cement, dog tooth calcite crystals and micritic cement overgrowth on
vuggs and fractures surface. .................................................................................................................................. 74
Figure 4.3.6. The reservoir area of the Karun-4 dam surrounded partly by the Kuh Sefid Anticline. The Pabdeh
Formation constitutes reservoir bed rock near dam location. This formation lithologically comprise impervious
succession of marlstone and marly limestone (2006). ........................................................................................... 75
Figure 4.3.7. The direction of 1 / Shortening at Karun-4 dam site. .................................................................... 76
Figure 4.3.8. Engineering geological section of the Karun-4 along Dam axis (after MG co., 2010). .................. 77
Figure 4.3.9. The reverse faults F. 15 and F. 17 (slickenside) at the right flank................................................... 78
Figure 4.3.10. The small scale repetitious reverse faults due to compression movements in the Asmari
Formation rocks the rigid layer of limestone embedded between two ductile layers of marlstone (northeastern
limb of the Kuh Sefid Anticline). .......................................................................................................................... 78
Figure 4.3.11. Stereographic projection of faults which are located on the dam axis of the Karun-4. A- Contour
plot, B- Major planes plot and C- Rosette plot. (Dips©, equal area projection-Schmidt net, lower hemisphere). 79
Figure 434.3.12.Stereographic projection of joints (discontinuity distribution) at the right flank of the Karun-4
dam site. A- Contour plot, B- Scatter plot and Rosette plot (Dips©, equal area projection-Schmidt net, lower
hemisphere). .......................................................................................................................................................... 81
Figure 4.3.13. Stereographic projection of joints (discontinuity distribution) at the left flank of the Karun-4 dam
site. A- Contour plot, B- Scatter plot and Rosette plot (Dips©, equal area projection-Schmidt net, lower
hemisphere). .......................................................................................................................................................... 82
Figure 4.4.1. The satellite image of the Marun dam site on the northern flank of the Khaviz Anticline. The
Marun rock fill dam constructed at Tange Takab (gorge) approximately 19 km northeast of Behbahan in
Khuzestan Province of Iran (Google Earth, European Technology, 2009). .......................................................... 83
Figure 4.4.2. The Marun rock fill dam constructed on the northern flank of the Khaviz Anticline. The various
parts of dam such as semi underground power plant, spillway, diversion tunnels and access road to the dam crest
can be seen. The closed red lines indicate some important instability with high risk of falling rock hazard. ....... 84
Figure 4.4.3. The geological map of Marun dam and power plant project in the Zagros Range of Iran. The dam
foundation is limestone, marly limestone, marlstone and dolomitic limestone of the Asmari Formation (after MG
co., 2010). .............................................................................................................................................................. 85
Figure 4.4.4. Lithological column of the Asmari Formation at the Marun dam site. The Asmari Formation
consists of 370 m limestone, dolomitic limestone, marly limestone and divided into three main units. ............... 86
Figure 4.4.5. Some karstic features due to acidic water dissolution in the Asmari Formation limestone. The
porosities mostly seem channel porosity, but in some places at intersection between bedding planes and
discontinuities, karstification is well developed because of limestone dissolution. .............................................. 88
Figure 4.4.6. The reservoir area of the Marun dam site that situated on northeast flank of the Khaviz Anticline.
The upper Asmari Formation limestone as main dam foundation and evaporite rocks of Gachsaran Formation
that constitute a part of reservoir area can be observed. ........................................................................................ 89
Figure 4.4.7. The major seismically active faults in the study area in the Zagros region. This map shows the
distribution of active faults and demonstrates the relationship between the slip vectors and compressive axis,
obtained from the determination of the focal mechanism of the earthquakes, and GPS velocities (after
International Institute of Earthquake Engineering and Seismology- Iran, 2003). ................................................. 90
viii
Figure 4.4.8. Panoramic view of the Khaviz Anticline and Marun dam location with the main faults and fracture
systems. The Keystone graben caused by extensional process at outer core of anticline during compressional
regime can be observed. ........................................................................................................................................ 91
Figure 4.4.9. The direction of 1 / Shortening at Marun dam site. ....................................................................... 92
Figure 4.4.10. Stereographic projection of joints at the Marun Dam. A- Contour plot, B- Rosette plot and CPole plot of discont inuities (Dips©, equal area projection-Schmidt net, lower hemisphere). .............................. 93
Figure 4.5.1. Satellite image of the Seymareh dam site on the northern flank of the Ravandi Anticline with a
northwest-southeast trend. The Seymareh concrete arch dam is constructed in the Seymareh river valley
approximately 106 km southeast of Ilam city at Ilam Province of Iran (Google Earth, European Technology
2009)...................................................................................................................................................................... 94
Figure 4.5.2. Aerial view of Seymareh dam site being constructed on the northern flank of the Ravandi
Anticline (after khoshboresh, 2007). ..................................................................................................................... 95
Figure 4.5.3. The Seymareh dam foundation rocks and associated structures such as diversion tunnels, spillway
and downstream cofferdam. The dam foundation rock is Asmari Formation limestone (2007). .......................... 96
Figure 4.5.4. The engineering geological map of the Seymareh dam and power plant project. Asmari Formation
constitutes the dam foundation rocks and comprise grey to light grey limestone, dolomitic limestone and marly
limestone Oligomiocene age (after MG co., 2010). .............................................................................................. 97
Figure 4.5.5. Lithological column of the Asmari Formation at the Seymareh dam site. The Asmari Formation
consists of 572 m cream to light grey limestone, dolomitic limestone, marly limestone and marlstone which is
divided into three main units. ................................................................................................................................ 98
Figure 4.5.6. The large cavities due to dissolution of limestone mainly along bedding planes downstream of the
dam axis. These features can be observed high on both flanks of the dam foundation (2007). .......................... 100
Figure 4.5.7. Some karstic features related to dissolution of limestone through discontinuity surfaces by
aggressive water with dimensions from 10 cm to metres (A, B) and cavities related to diagenetic process with
small dimensions (B, C). ..................................................................................................................................... 101
Figure 4.5.8. The major seismically active faults in the study area in the Zagros region. This map shows the
distribution of active faults and demonstrates the relationship between the slip vectors and compressive axis
obtained from the solution of the focal mechanism of the earthquakes, and GPS velocities (after International
Institute of Earthquake Engineering and Seismology- Iran, 2003)...................................................................... 102
Figure 4.5.9. Panoramic view of the Seymareh river valley at the Ravandi Anticline with the Seymareh dam
location on the northern flank of the anticline. The reservoir with 3 215 million cubic metres volume and
upstream cofferdam as well as the Manuran Anticline are also shows. .............................................................. 103
Figure 4.5.11. The engineering geological cross section of the Asmari Formation along the dam axis. The
Asmari limestone units were subjected to faulting and folding due to compressional stresses. The faults are
mainly reverse faults with small displacements. The exploratory boreholes BH5, BH7, BH9, BH10, BH33 and
BH34 indicate the RQD and permeability values of the rock mass (after MG co., 2009). .................................. 104
Figure 4.5.10. Small scale normal faults (key stone graben) on the right side of the Seymareh River valley.
These structures occurr in the area around the anticline axis where extensional area was created at the top, then
followed by vertical displacement of blocks due to gravity. ............................................................................... 104
Figure 4.5.12. Stereographic projection of faults (general orientation of small- scale faults) at the two abutments
of dam site A- Contour plot, B- Rosette plot, and C- Pole plot of faults with field stress directions (Dips©, equal
area projection-Schmidt net, lower hemisphere). ................................................................................................ 105
Figure 4.5.13. The direction of 1 / Shortening at Seymareh dam site. .............................................................. 106
Figure 4.5.14. Stereographic projection of joints (discontinuities distribution) at Seymareh dam site A- Contour
plot, B- Rosette plot, and C- Pole plot of joints (Dips©, equal area projection-Schmidt net, lower hemisphere).
............................................................................................................................................................................. 108
Figure 4.6.1. Satellite image of the Salman Farsi dam site and surrounding area on the northern flank of the
Changal Anticline (Google Earth, European Technology 2006). ........................................................................ 109
Figure 4.6.2. Salman Farsi (Ghir) dam is a concrete arch gravity dam 125 m high and is under construction on
the Ghareh Agahaj River. .................................................................................................................................... 110
Figure 4.6.3. Simplified geological mapof the Salman Farsi dam and power plant project. Several small-scale
strike slip faults. (after MG co., 2009). ............................................................................................................... 111
Figure 4.6.4. Lithological column of the Asmari Formation and petrographic analysis interpretations at Salman
Farsi (Ghir) dam. ................................................................................................................................................. 112
Figure 4.6.5. Some karstic features due to dissolution of limestone along discontinuity surfaces in the upper part
of the middle unit of the Asmari Formation. These features constitute a 3D network of channels, which
somewhere converge into huge caverns. ............................................................................................................. 113
Figure 4.6.6. The engineering geological section of the Asmari Formation at the right and left flanks of the
Salman Farsi dam. The exploration and grouting galleries, limit of cut-off curtain and section of diversion tunnel
can be observed (after MG co., 2009). ................................................................................................................ 114
ix
Figure 4.6.7. Several channels related to cavern development in the right flank. The bedding planes and Js.1 are
mainly responsible for cave development. .......................................................................................................... 116
Figure 4.6.8. Schematic presentation of the longitudinal section of the grout curtain and approximate positions
of cavities at the Salman Farsi dam (after Stucky-Electrowatt, 2001)................................................................. 118
Figure 4.6.9. The geological map and section of Golshani Cave in the right flank of the Salman Farsi dam. (after
Stucky-Electrowatt, 2001). .................................................................................................................................. 118
Figure 4.6.10. The southern part of the reservoir area of the Salman Farsi dam project on the northern limb of
the Changal Anticline. The bedrock consists of almost impermeable rock successions of the Fars Group. The
Karbasi Anticline, which forms the northeastern boundary of the reservoir can be seen as well (2007). ........... 119
Figure 4.6.11. The major seismically active faults in the study area. The map shows the distribution of active
faults and demonstrates the relationship between the slip vectors and compressive axis, obtained from the
solution of the focal mechanism of earthquakes, and GPS velocities (International Institute of Earthquake
Engineering and Seismology- Iran, 2003). .......................................................................................................... 120
Figure 4.6.12. The Salman Farsi dam site is situated on the northern flank of the Changal Anticline which
follows the Zagros trend. The Karbasi Anticline represents the northern rim and the Changal Anticline represents
the southern rim of the future reservoir (2007) ................................................................................................... 121
Figure 4.6.13. The Dareh Siah Thrust Fault cuts the core of the Changal Anticline then continues to the
northwest of the dam site and caused the Asmari Formation thrusted on to the Razak evaporites Formation. ... 122
Figure 4.6.14. Stereographic projection of joints (discontinuity distribution) of the Salman Farsi dam foundation
rocks. A- Contour plot, B- Rosette plot, and C- Scatter plot of joints (Dips©, equal area projection-Schmidt net,
lower hemisphere). .............................................................................................................................................. 124
Figure 4.6.15. Stereographic projection of faults (general orientation of small- scale faults) at the two abutments
of the dam site A- Contour plot, B- Rosette plot, and C- Scatter plot of faults (Dips©, equal area projectionSchmidt net, lower hemisphere). ......................................................................................................................... 125
Figure 4.6.16. The direction of 1 / Shortening at Salman Farsi dam site. ......................................................... 126
Figure 4.7.1. The minimum/maximum porosity values based on petrographical analysis of rock foundations at
Karun-3 (K-3), Karun-4 (K-4), Seymareh (Se), Marun (M) and Salman Farsi (Sa) dam projects. L (lower), M
(middle), U (upper).............................................................................................................................................. 127
Figure 4.7.2. Ternary porosity type plot (ternary diagrams of carbonate pore types) provides information on the
shapes and origin of pore systems. The plots are based on quantitative data derived from point counting of thin
sections. ............................................................................................................................................................... 129
Figure 4.8.1. Block diagram showing three successive formations (Pabdeh, Asmari and Gachsaran) at the
Zagros folded belt and relative dam site localities at the two flanks of anticlines. .............................................. 131
Figure 4.8.2. The karstification model at the northern flank of anticlines in the Zagros folded belt and the role of
the Gachsaran/ Razak Formation evaporites on karstification of the Asmari limestone. .................................... 132
Figure 4.8.3. Schematic geological section through the Asmari-Gachsaran/Razak contact and evolution of
karstic collapse feature. The dissolution of the Gachsaran/Razak evaporites (gypsum, anhydrite, salt, marl) due
to high solubility of evaporites sequence (solution-collapse structures). The water bearing acid (H2SO4 solutions)
will be outcome of the process, which can dissolve the Asmari Formation limestone and accelerate the
karstification process. .......................................................................................................................................... 133
Figure 4.8.4. Closed depression in red marls bearing gypsum of Gachsaran Formation (A). Karst development in
Razak evaporites formation at the Salman Farsi dam site. Dissolution is mostly pronounced along joints and
bedding planes (B)............................................................................................................................................... 134
Figure 4.8.5. Some solution- collapse structures in Gachsaran Formation due to high solubility and erodible
evaporite rocks. Gypsum-dissolution at the region generates sulphate-rich water then collapse of overlying rocks
into cavities occurs. ............................................................................................................................................. 135
Figure 4.8.6. The distribution of the Gachsaran evaporites rocks (mainly gypsum) at reservoir area of the Marun
dam site. The surface karstification and weathering features can be observed as well. The residential structures
are constructed almost on karstified rocks of the Gachsaran Formation (2007). ................................................. 136
Figure 4.8.7. Illustrating common Ion, foreign Ion and Ionic strength effects. Increase of gypsum solubility with
addition of NaCl (after Ford and Williams, 2007)............................................................................................... 136
Figure 5.2.1. Geological section along the diversion tunnel at the Karun-3 Dam (after MG co., 1993). ........... 138
Figure 5.2.2. Contour plot and major plane plots of discontinuity sets in the diversion tunnel. ......................... 139
Figure 5.2.3. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 59 in the lower unit of the Asmari Formation. ... 141
Figure 5.2.4. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 71 in the lower unit of the Asmari Formation. ... 141
Figure 5.2.5. Multi view of the diversion tunnel. The shape, dimensions and specifications of wedges because of
intersecting major discontinuity sets Js.1 (bedding planes), Js.2 and Js.3 in diversion tunnel at the Karun-3 Dam.
............................................................................................................................................................................. 142
x
Figure 5.2.6. Rock support arrangement in good quality rock mass at 15 m excavated diameter of diversion
tunnel (A- 2D and B- 3D views). ........................................................................................................................ 143
Figure 5.2.7. The finite element mesh of normal and shear stresses for all possible wedge because of
intersection of discontinuities at diversion tunnel. The critical wedges based on distribution of shear stress and
the shapes of wedges are A-B. In the other cases, the instabilities will be very small and local. A-B (Js.1, Js.2,
Js.3), C-D (Js.1, Js.2, Js.4), E-F (Js.1, Js.3, Js.4), G-H (Js.2, Js.3, Js.4). ............................................................. 144
Figure 5.2.8. Geological section along the hydropower tunnels axis and gate shaft (after MG co., 1993). ....... 145
Figure 5.2.9. Contour plot and major plane plots of discontinuity sets at the hydropower tunnels (Dips©, equal
area projection-Schmidt net, lower hemisphere). ................................................................................................ 146
Figure 5.2.10. The shape dimensions and specifications of wedges because of intersecting major discontinuities
in the hydropower tunnel of Karun-3 Dam (dia.15 m). ....................................................................................... 147
Figure 5.2.11. Rock support arrangement A (2D view) and B (3D view) of the Lower Asmari Formation (4a1,
4a2, 4a3, 4a4) in good quality rock mass in 15 m diameter of the power tunnel. ............................................... 148
Figure 5.2.12. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 39 in the upper unit of the Asmari Formation. ... 150
Figure 5.2.13. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 62 in the upper unit of the Asmari Formation. ... 150
Figure 5.2.14. General Geological Strength Index (GSI) chart, for jointed rock masses (Hoek and Brown 1997,
Hoek and Karzulovic, 2001). The shaded area is indicative of distribution of geological strength index of various
rock mass units of the Asmari Formation at the Karun-3 dam. ........................................................................... 151
Figure 5.2.15. The lithological units and engineering rock mass characterization of the Asmari Formation at the
Karun-3 dam. ....................................................................................................................................................... 152
Figure 5.2.16. Developed section of the grout curtain of the Karun-3 dam (MG co. 1989). .............................. 154
Figure 5.3.1. The diversion tunnel at outlet and down stream coffer dam, during the heavy flood 2006 (left).
Diversion tunnel with temporary support elements. The final reinforced concrete lining has been done in the
lower part of tunnel (right). ................................................................................................................................. 156
Figure 5.3.2. The engineering geological section along the diversion tunnel. This tunnel with over 600 m
excavated in the Pabdeh and lower unit of Asmari Formations (after MG co., 1989). ....................................... 157
Figure 5.3.3. All possible rock wedges due to intersection of the major joint sets, Js.1, Js.3 and bedding planes in
the diversion tunnel. A- Perspective view, B- Side view of tunnel showing unstable wedges, C- (2D view) and D
(3D view) of the Rock support arrangement of the lower Asmari Formation in good quality rock mass. .......... 158
Figure 5.3.4. The finite elements mesh of normal and shear stresses for all possible wedges because of
intersection of discontinuities in the diversion tunnel. ........................................................................................ 159
Figure 5.3.5. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 56 in the lower unit of the Asmari Formation. ... 160
Figure 5.3.6. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 66 in the lower unit of the Asmari Formation. ... 161
Figure 5.3.7. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 27 in the middle unit of the Asmari Formation. . 162
Figure 5.3.8. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 44 in the middle unit of the Asmari Formation. . 162
Figure 5.3.10. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 36 in the upper unit of the Asmari Formation. ... 164
Figure 5.3.9. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 27 in the upper unit of the Asmari Formation. ... 164
Figure 5.3.11. General Geological Strength Index (GSI) chart, for jointed rock masses (Hoek and Brown 1997,
Hoek and Karzulovic, 2001). The shaded area is indicative of distribution of geological strength index of various
rock mass units of the Asmari Formation at the Karun-4 dam. ........................................................................... 165
Figure 5.3.12. The lithological units and engineering rock mass characterization of the Asmari Formation at the
Karun-4 dam. ....................................................................................................................................................... 166
Figure 5.4.1. The Marun dam site and other accessory structures. The two diversion tunnels, power tunnels,
spillway at the left flank and rock fill dam body can be observed. The diversion and power tunnels pass through
all three units of the Asmari succession but the spillway structure is mainly located in the lower and middle
units. .................................................................................................................................................................... 167
Figure 5.4.2. The dimensions, geometry and structural specifications of wedges because of intersecting major
joint sets of Js.3, Js.4 and Js.1 (bedding planes) in the diversion tunnel at the Marun dam. A- Perspective view,
B- Side view of tunnel, showing potentially unstable wedges and C- Rock support elements arrangement for the
Asmari Formation limestone. .............................................................................................................................. 169
Figure 5.4.3. The finite elements mesh of normal and shear stresses for all possible wedges due to the
intersection of discontinuities (Js.3, Js.4 and bedding planes at diversion tunnel. Here the critical wedges based
xi
on distribution of shear stress can be observed with A- normal stress distribution, B, C and D are shear stress
distributions in perspective view, side view and top view of tunnel respectively. The instability of wedge 8 can
be observed in the top view. ................................................................................................................................ 170
Figure 5.4.5. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 71 in the lower unit of the Asmari Formation. ... 171
Figure 5.4.4. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 54 in the lower unit of the Asmari Formation. ... 171
Figure 5.4.6. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 51 in the middle unit of the Asmari Formation. . 173
Figure 5.4.7. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 66 in the middle unit of the Asmari Formation. . 173
Figure 5.4.8. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 46 in the upper unit of the Asmari Formation. ... 175
Figure 5.4.9. Relationship between major and minor principal stresses also normal and shear stresses for HoekBrown and equivalent Mohr-Coulomb criteria for GSI 62 in the upper unit of the Asmari Formation. ............. 175
Figure 5.4.10. General Geological Strength Index (GSI) chart, for jointed rock masses (Hoek and Brown 1997,
Hoek and Karzulovic, 2001). The shaded area is indicative of distribution of geological strength index of various
rock mass units of the Asmari Formation at the Marun dam. .............................................................................. 176
Figure 5.4.11. The lithological units and engineering rock mass characterization of the Asmari Formation at the
Marun dam. ......................................................................................................................................................... 177
Figure 5.5.1. Relationship between the major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 51 in the lower Asmari Formation. ..................... 179
Figure 5.5.2. Relationship between the major and minor principal stresses as well as the normal and shear
stresses for the Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 56 in the lower Asmari Formation.
............................................................................................................................................................................. 179
Figure 5.5.3. Engineering geological section along the diversion tunnels. These tunnels pass through the middle
and upper Asmari Formation limestone and are 473 m and 395 m long with 10.5 m and 8.2 m diameter
respectively (after MG co., 2009). ....................................................................................................................... 180
Figure 5.5.4. Downstream view of the Seymareh dam and some accessory structures such as diversion tunnels,
spillway and down stream cofferdam. Some major joint sets and faults with small displacement at right bank can
be observed. ......................................................................................................................................................... 181
Figure 5.5.5. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 51 in the middle unit of the Asmari Formation. . 183
Figure 5.5.6. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 69 in the middle unit of the Asmari Formation. . 183
Figure 5.5.7. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 47 in the upper unit of the Asmari Formation. ... 185
Figure 5.5.8. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 64 in the upper unit of the Asmari Formation. ... 185
Figure 5.5.9. Dimensions, geometry and structural specifications of wedges resulted by intersection of major
joint sets Js.1, Js.2 and bedding planes (Js.4) at 10.5 m diameter diversion tunnel of the Seymareh dam. APerspective view, B- Side view of tunnel showing potentially unstable wedges, C (2D view) and D (3D view) of
rock support arrangement of the Asmari Formation limestone in the fair quality rock. ...................................... 186
Figure 5.5.10. Dimensions, geometry and structural specifications of wedges formed by intersecting major joint
sets Js.1, Js.3 and bedding planes (Js.4) in the diversion tunnel. A- Perspective view, B- Top view of tunnel
showing potentially unstable wedges. ................................................................................................................. 187
Figure 5.5.11. Finite element mesh of normal and shear stresses for all possible wedges due to intersection of
discontinuities in the diversion tunnel. The critical wedges based on distribution of shear stress and the shape of
the wedge is A-B (Js.1, Js.2 and Js.4 or bedding planes). . ................................................................................. 188
Figure 5.5.12. General Geological Strength Index (GSI) chart, for jointed rock masses (after Hoek and Brown,
1997, Hoek and Karzulovic, 2001). The shaded area is indicative of the distribution of the geological strength
index of the various rock mass units of the Asmari Formation at the Seymareh dam. ........................................ 189
Figure 5.5.13. The lithological units and engineering rock mass characterization of the Asmari Formation at the
Seymareh dam. .................................................................................................................................................... 190
Figure 5.6.1. Dimensions, geometry and structural specifications of wedges due to intersecting major joint sets
Js.1, Js.3 and bedding planes in the diversion tunnel at the Salman Farsi dam. A- Perspective view, B- Side view
of tunnel showing potentially unstable wedges, C (2D view) and D (3D view) of rock support arrangement in the
middle Asmari limestone of fair quality rock mass. ............................................................................................ 192
xii
Figure 5.6.2. Finite elements mesh of normal and shear stresses for all possible wedges because of intersection
of discontinuities in the diversion tunnel. Critical wedges are based on the distribution of shear stress and the
shapes of wedges in A-B and G-H. In the other cases, the instabilities will be small and local........................ 1944
Figure 5.6.3. Pattern and arrangement of rock support elements in good quality rock of the middle unit of the
Asmari Formation. The support elements will be spot bolting and 30 mm shotcrete in the roof and in the sides if
needed.................................................................................................................................................................. 195
Figure 5.6.4. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 45 in the middle unit of the Asmari Formation. . 197
Figure 5.6.5. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 62 in the middle unit of the Asmari Formation. . 197
Figure 5.6.6. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 35 in the lower unit of the Asmari Formation. ... 198
Figure 5.6.7. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 20 in the upper unit of the Asmari Formation. ... 200
Figure 5.6.8. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 37 in the upper unit of the Asmari Formation. ... 200
Figure 5.6.9. General Geological Strength Index (GSI) chart, for jointed rock masses (Hoek and Brown 1997,
Hoek and Karzulovic, 2001). The shaded area is indicative of the distribution of the geological strength index of
the various rock mass units in the Asmari Formation at the Salman Farsi dam. ................................................. 201
Figure 5.6.10. The lithological units and engineering rock mass characterizations of the Asmari Formation at the
Salman Farsi (Ghir) dam project. ........................................................................................................................ 202
Figure 6.1. Schematic geological cross section of Asmari Formation limestone at the Zagros folded belt. The
situation of the dam sites on each flank can be observed as well. ....................................................................... 203
Figure 6.2. A simple block diagram of Asmari formation limestone at the Zagros folded belt. Southern flank
clearly indicate much more gradient of strata between 70°- 90°, on contrary the northern flank has dipping
between 20° to 50° toward the northeast therefore due to less curvature of strata fewer tectonic features can be
expected. .............................................................................................................................................................. 204
Figure 6.3. Histogram of RQD values for the Asmari formation limestone, calculated for Karun-3 (K-3), Karun4 (K-4), Seymareh (Se), Marun (M), and Salman Farsi (Sa) dam sites. .............................................................. 205
Figure 6.4. The different geological condition of dam localities, (A) Seymareh, Marun, Salman Farsi in the
northern flank and (B) Karun-3, Karun-4 in the southern flank of the anticlines. The situation of dam body/cutoff curtain and reservoir on one hand and distribution of the Pabdeh, Asmari and Gachsaran formations with
various permeabilities on the other hand is of considerable matter in the point of view permeability and
watertightness. ..................................................................................................................................................... 206
Figure 6.5. The stereographic projection of major discontinuity sets in the Asmari formation limestones at the
various dam locations. The slope stability based on intersections of major joint sets and rock slope faces
indicates various kinds of rock failures such as planar, wedge and toppling in the area. .................................... 209
Figure 6.6. The schematic block diagrams showing geological conditions of the Asmari formation limestones as
the main dam foundation rocks and dam localities in northern flank sites (A- Seymareh, Marun, Salman Farsi)
and in southern flank sites (B- Karun-3, Karun-4). They are typically indicating various types of unstable slopes.
In case A, planar and wedge failures toward the reservoir, and wedged, toppling failures toward the gorge. In
case B, wedge and toppling failures toward the reservoir and gorge and planar failure toward the gorge will be
expected. .............................................................................................................................................................. 211
Figure 6.7. The typical block diagram and geological section of the Asmari and Gachsaran formations in the
Zagros folded belt and the possibility of land slide hazard after impoundment of the reservoir. In general rock
sliding adjacent to the dam locations toward the reservoir, will mainly be planar (in Asmari limestones) and
rotational to planar (in Gachsaran evaporites). As a result of rock failure the Seymareh river bed was displaced
about 1000 m toward the northeast during historic times. ................................................................................... 212
Figure 6.8. Rockfall hazard at Marun dam site in successive stages on the left flank (A, B) and right flank (C,
D). The power plant and access roadways are subjected to rock fall hazard every day. ..................................... 213
Figure 6.9. Catchment fence or Barrier fence specifications and installation procedure (after Geobrugg AG
protection system, Switzerland, 2010). ............................................................................................................... 215
Figure 6.10. Energy absorbing ring (A), when subjected to impact loading the ring deforms plastically (B) and
absorbs the energy of the boulder. (C) Impact sentinel sensors check the status of rockfall protection systems and
set off an alarm (Geobrugg AG protection system- Switzerland, 2010). ............................................................ 215
Figure 6.11. Rockfall control by free hanging mesh drape and its installation. It is commonly used for permanent
slopes. It can be used effectively at the right flank of the Marun dam (after Fookes and Sweeney, 1976). ........ 216
Figure 6.12. Systematic rock bolting (60 mm in diametre) of rock slope face at spillway- right flank of Karun-4
dam (2007). ......................................................................................................................................................... 217
xiii
Figure 6.13. Rock slope failure after application of unreinforced shotcrete on marl units of the Asmari
Formation. The marls or such rocks need to be stablized by reinforced shotcrete due to ductility and
deformability of the rock mass. The vertical extensional joints and fractures due to gravity movement of the rock
mass can clearly be observed (Karun-3 dam site, entrance gate, 2007). ............................................................. 217
Figure 6.14. Steel fibre types available on the North American market. (after Wood et al., 1993). (Note: all
dimensions are in mm). ....................................................................................................................................... 218
Figure 6.15. Histogram of RMR values for the Asmari formation limestone, calculated for Karun-3 (K-3),
Karun-4 (K-4), Seymareh (Se), Marun (M), and Salman Farsi (Sa) dam sites. ................................................... 220
Figure 6.16. Histogram of UCS values for the Asmari formation limestone, calculated for Karun-3 (K-3),
Karun-4 (K-4), Seymareh (Se), Marun (M), and Salman Farsi (Sa) dam sites. ................................................... 221
Figure 6.17. Histogram of GSI values for the Asmari formation limestone, calculated for Karun-3 (K-3), Karun4 (K-4), Seymareh (Se), Marun (M), and Salman Farsi (Sa) dam sites. .............................................................. 221
Figure 6.18. Geological Strength Index (GSI) chart, for jointed rock mass (Hoek and Brown 1997, Hoek and
Karzulovic, 2001, Marinos and Hoek, 2005). The shaded areas indicate the distribution of geological strength
index values of the various rock mass units of the Asmari Formation. ............................................................... 223
Figure 6.19. Relationship between RMR and rock cutting rate. (after Fowell and Johnson, 1982). .................. 227
Figure 6.20. Relationship between net allowable bearing capacity and Rock Mass Rating (after Mehrotra, 1993)
............................................................................................................................................................................. 228
xiv
List of Tables
Table 1.1. Rainfall in the major basins in Iran (Bureau of Operation and Maintenance of Dams and Irrigation
Networks, 1995). ..................................................................................................................................................... 7
Table 2.1. Asmari Formation assemblage zones (after Adams and Bourgeois, 1965). ......................................... 35
Table 3.1. Correlation between RQD and rock mass quality (after Deere, 1968)……………… …………………………
37
Table 3.2. Major rock mass classification/characterisation systems (midified after Palmstrom 1995) ................. 39
Table 3.3. Rock Mass Rating (RMR) System (after Bieniawski 1989). ................................................................ 40
Table 3.4. Guidelines for excavation and support of 10 m span rock tunnels in accordance with the RMR system
(After Bieniawski 1989). ....................................................................................................................................... 41
Table 3.5. Classification of individual parameters used in the Tunneling Quality Index Q (after Barton et al.,
1974)...................................................................................................................................................................... 44
Table 3.6. Excavation support ratio – ESR for various excavation categories (Barton, 1974). ............................. 46
Table 3.7. Adjustments rating for joints (Romana, 1993). .................................................................................... 51
Table 3.8. Adjustment factor due to method of excavation of slopes (Romana, 1993). ........................................ 51
Table 3.9. The SMR classes (Romana, 1993). ...................................................................................................... 51
Table 3.10. FRHI worksheet (after Singh, 2004) .................................................................................................. 53
Table 3.11. Rock fall hazard classification (after Singh, 2004) ............................................................................. 54
Table 4.2.1. The technical specifications of the Karun-3 dam and power plant project. ....................................... 58
Table 4.2.2. Bedrock formations present at the Karun-3 dam (after James and Wynd, 1965). ............................. 59
Table 4.2.3. Bedding and joint sets orientation at the Karun-3 Dam site (after MG co., 1993). ........................... 62
Table 4.2.4. Summary of Faults near the Karun-3 dam site (Berberian, 1976). .................................................... 67
Table 4.3.1. The technical specifications of the Karun-4 dam and power plant project (MG co., 1995- 1997). ... 70
Table 4.3.2. Geological formations around the project area. ................................................................................. 71
Table 4.3.3. The range of variation of porosity values classified on a logarithmic scale. (Cherenyshev, Dearman,
1991): .................................................................................................................................................................... 73
Table 4.3.4. The porosity% and permeability of the Asmari Formation units....................................................... 73
Table 4.3.5. The faults identifications at the Kaun-4 dam axis. ............................................................................ 77
Table 4.4.1. Marun dam and power plant project specifications (after MG co., 1986). ........................................ 84
Table 4.4.2. Geological formations around project area. ....................................................................................... 85
Table 4.4.3. The quantity and quality criteria for permeability classification (Lewis et al., 2006). ...................... 87
Table 4.4.4. The range of variation of porosity values classified on a logarithmic scale. (Cherenyshev, Dearman,
1991)...................................................................................................................................................................... 87
Table 4.4.5. The porosity and permeability lavues of the Asmari Formation units. .............................................. 88
Table 4.5.1. The technical specifications of the Seymareh dam and power plant project. .................................... 96
Table 4.5.2. The geological formations at the Seymareh dam site. ....................................................................... 97
Table 4.6.1. Salman Farsi dam and power plant project specifications. .............................................................. 110
Table 4.6.2. A summary of the principal formations in the project area. ............................................................ 111
Table 4.7.1. The petrographical analysis of five dam foundation rocks .............................................................. 128
Table 5.2.1. Discontinuity sets in the diversion tunnel. ....................................................................................... 138
Table 5.2.2. Rock Quality Designation (RQD) assessment of the Asmari Formation at the Karun-3 Dam. ....... 139
Table 5.2.3. Assessment of Rock Mass Rating for the Asmari Formation (4a1, 4a2, 4a3). ................................ 139
Table 5.2.4. Rock support types for units 4a1, 4a2, and 4a3 in the diversion tunnel. ......................................... 140
Table 5.2.5. The rock mass strength in the Lower Asmari unit. .......................................................................... 140
Table 5.2.6. The rock wedge specifications at the diversion tunnel resulted by Js.1, Js.2 and Js.4. .................... 143
Table 5.2.7. Summary of discontinuity data at the Hydropower tunnels. ............................................................ 146
Table 5.2.8. Assessment of Rock Mass Rating for the Lower Asmari Formation (4a1, 4a2, 4a3, 4a4) in the
hydropower tunnels. ............................................................................................................................................ 146
Table 5.2.9. Rock support types for units 4a1, 4a2, 4a3 and 4a4 in the hydropower tunnels. ............................. 146
Table 5.2.10. The rock wedge specifications in the hydropower tunnel resulted by three joint sets. .................. 148
Table 5.2.11. Assessment of Rock Mass Rating for the Upper Asmari (As.2). .................................................. 149
Table 5.2.12. The rock mass strength in the Upper Asmari unit. ........................................................................ 149
Table 5.2.13. Permeability (K) values classification. .......................................................................................... 153
Table 5.2.14. Hydraulic conductivity of the Asmari and Pabdeh formations in the Karun-3 Dam. .................... 153
Table 5.3.1. Major discontinuity sets and their specifications. ............................................................................ 156
Table 5.3.2. Assessment of Rock Mass Rating for the Asmari Formation (Lower unit). .................................... 157
Table 5.3.3. Rock support types in the diversion tunnel………...…..………………………………………………………………………………....157
.
………… ……… ……… ……… ……… ……… ……… ……… ….
Table 5.3.4. The rock wedge specifications in the diversion tunnel. ................................................................... 160
xv
Table 5.3.5. The rock mass strength in the Lower Asmari unit. .......................................................................... 160
Table 5.3.6. Assessment of Rock Mass Rating for the Middle Asmari Formation (Middle unit). ...................... 161
Table 5.3.7. The rock mass strength in the Middle Asmari unit. ......................................................................... 162
Table 5.3.8. Assessment of Rock Mass Rating for the Asmari Formation (Upper unit). .................................... 163
Table 5.3.9. The rock mass strength in the Upper Asmari unit. .......................................................................... 163
Table 5.4.1. Major discontinuity sets and their specifications at the Marun dam site. ........................................ 168
Table 5.4.2. Assessment of Rock Mass Rating for the Asmari Formation (Lower unit). .................................... 168
Table 5.4.3. Rock support types for the middle unit in the diversion tunnel (Bieniawski, 1984)…...…………………….168
Table 5.4.4. The rock wedge specification in the diversion tunnel ..................................................................... 170
Table 5.4.5. The rock mass strength in the lower Asmari unit. ........................................................................... 171
Table 5.4.6. Assessment of Rock Mass Rating for the Asmari Formation (Middle unit).................................... 172
Table 5.4.7. The rock mass strength in the Middle Asmari unit. ......................................................................... 172
Table 5.4.8. Assessment of Rock Mass Rating for the Asmari Formation (Upper unit). .................................... 174
Table 5.4.9. The rock mass strength in the Upper Asmari unit. .......................................................................... 174
Table 5.5.1. Major discontinuity sets and their specifications. ............................................................................ 178
Table 5.5.2. Assessment of Rock Mass Rating for the Lower Asmari unit (As.1). ............................................. 178
Table 5.5.3. The rock mass strength in the Lower Asmari unit. .......................................................................... 179
Table 5.5.4. Assessment of Rock Mass Rating for the Middle Asmari unit (As.2). ............................................ 181
Table 5.5.5.Rock support types for good and fair rock mass in the diversion tunnel ………………………………… 181
Table 5.5.6. The rock mass strength in the Middle Asmari unit. ......................................................................... 182
Table 5.5.7. Assessment of Rock Mass Rating for the Upper Asmari unit (As.3). ............................................. 184
Table 5.5.8.The rock mass strength in the Upper Asmari unit ............................................................................ 184
Table 5.5.9. The rock wedge specifications in the diversion tunnel resulted by Js.1, Js.2 and Js.4 .................... 186
Table 5.5.10. The rock wedge specifications in the diversion tunnel resulted by Js.1, Js.3 and Js.4. ................. 187
Table 5.6.1. Major discontinuity sets and their specifications. ............................................................................ 191
Table 5.6.2. Assessment of Rock Mass Rating for the Asmari Formation (Middle unit).................................... 191
Table 5.6.3. Rock support types for the middle unit in the diversion tunnel…..…………………………………………191
Table 5.6.4. The rock wedge specifications at the diversion tunnel resulted by joint sets Js.1, Js.3 and bedding
planes. .................................................................................................................................................................. 193
Table 5.6.5. The rock mass strength in the Middle Asmari unit. ......................................................................... 196
Table 5.6.6. Assessment of Rock Mass Rating for the Asmari Formation (Lower unit). .................................... 197
Table 5.6.7. The rock mass strength in the Lower Asmari unit. .......................................................................... 198
Table 5.6.8. Assessment of Rock Mass Rating for upper unit of the Asmari Formation. ................................... 199
Table 5.6.9. The rock mass strength of the Upper Asmari unit. .......................................................................... 200
Table 6.1. The permeability condition of various unit of the Asmari Formation at dam localities. .................... 205
Table 6.2. The SMR values for various units of the Asmari Formation rocks in the study area. ........................ 208
Table 6.3. Rock Fall Hazard Index score assessment at left bank……………………………………………………………..…….210
Table 6.4. Rock Fall Hazard Index score assessment at right bank………………….….......…...……………………………….………...210
Table 6.5. The engineering rock mass properties of the Asmari Formation at the different dam sites. ............... 222
Table 6.6. Adjusting factor for dam stability after joints orientation (after Bieniawski and Orr, 1976) ............. 224
Table 6.7. Adjusting factors (RSTA) for the stability according to joint orientation (after Romana, 2003) .......... 224
Table 6.8. DMR evaluation of dam foundation rocks of five dam sites. ............................................................. 225
Table 6.9. The cuttability rates of the Asmari formation limestone based on Fowell and Johnson (1982)
experimental method. .......................................................................................................................................... 227
Table 6.10. Net allowable bearing capacity according to RMR values (after Mehrotra, 1993). ......................... 228
Table 6.11. The RMR values of the Asmari formation limestone ....................................................................... 228
xvi
Chapter 1
Introduction
1.1. Introduction
Most of Iran is arid or semi-arid with annual precipitation averaging about 240 mm or onethird of the world average (one-third of all precipitation in Iran occurs in the Caspian Sea
region in the north). Iran's land surface covers 165 million hectares, more than half of which
is not appropriate for cultivation. A total of 11.5 million hectares is under cultivation at any
time, of which 3.5 million hectares were irrigated in 1987, and the rest watered by rain
(U.S.Library of Congress, 1987). Only 10 percent of the country receives adequate rainfall
for agriculture; most of this area is in western Iran. Seasonal rainfall intensifies the water
shortage. The rainy season occurs between October and March, leaving the land parched for
the remainder of the year. In most parts of the world with such conditions (e.g. Central
Australia), there is no agriculture. Still, for most of its history, Iran has been primarily an
agricultural economy. Animal husbandry was possible until recently only by nomadic
pastoralism, the flocks moving at fixed seasons to new pastures, while crop farming was
mainly dependent on the qanat system (U.S.Library of Congress, 1987).
Iran's rivers are characterized by seasonal variations in flow. The Karun River and other
rivers passing through Khuzestan Province (in the southwest at the head of the Persian Gulf)
carry water during periods of maximum flow that is ten times the amount borne in dry
periods. Several of the government's dam projects are on these rivers (Figure 1.1). In
numerous localities, there may be no precipitation until sudden storms, accompanied by heavy
rains, dump almost the entire year's rainfall in a few days often causing floods and local
damage. The runoffs are so rapid that they cannot be used for agricultural purposes
(U.S.Library of Congress, 1987).
Water shortages are compounded by the unequal distribution of water. Near the Caspian
Sea (north), rainfall averages about 1280 mm per year, but in the Central Plateau and in the
lowlands to the south it seldom exceeds 100 mm to 120 mm, far below the 260 mm to 310
mm usually required for dry farming (U.S.Library of Congress, 1987).
Scarcities of water and of the means for making use of it have constrained agriculture since
ancient times. To make use of the limited amounts of water, the Iranians centuries ago
developed man-made underground water channels called qanats that are still in use. They
are usually located at the foot of a mountain and are limited to sloping land. A qanat taps
water that has seeped into the ground and channels it via straight tunnels in such a way to
surface in proximity to village crops (U.S.Library of Congress, 1987). The main advantage of
the qanat is that its underground location prevents most of the evaporation to which water
carried in surface channels is subjected. In addition, the qanat is preferable to the modern
power-operated deep wells because it draws upon underground water located far from the
villages. The main disadvantages of the qanat are the costs of construction and maintenance
and a lack of flexibility; the flow cannot be controlled, and water is lost when it is not being
used to irrigate crops (U.S.Library of Congress, 1987). In the late 1980s, an estimated 60,000
qanats were in use, and new units were still being dug (although not in western Iran, where
rainfall is adequate). To assist villagers, the government undertook a program to clean many
qanats after the revolution in 1979. Qanat water is distributed in various ways: by turn, over
specified periods; by division into shares; by damming; and by the opening of outlets through
which the water flows to each plot of land. So important is the qanat system to the
agricultural economy and so complex is the procedure for allocating water rights (which are
inherited) that a large number of court cases regularly deal with adjudication of conflicting
claims (U.S.Library of Congress, 1987).
Construction of large reservoir dams since World War II has made a major contribution to
water management for both irrigation and industrial purposes. Dam construction has centered
in the southwest of Iran in rivers flowing from the Zagros Mountains (e.g. Karun, Marun,
4
Karkheh, Seymareh and Dez Rivers). The upper courses flow in parallel stretches before
cutting through the surrounding mountains in extremely narrow gorges called tangs
(U.S.Library of Congress, 1987). The terrain in Khuzestan provides good dam sites and
government set up the Khuzestan Water and Power Authority in 1959 to manage natural
resources in that province. All economic development plans emphasized the need to improve
water supplies and reservoirs so as to improve crop production (U.S.Library of Congress,
1987). Large reservoirs were built throughout the country, beginning with the Second
Development Plan with first dams built on the Karaj, Sefid (north), and Dez Rivers
(southwest).
The first of the major dams had a significant impact on the Iranian economy. Completed in
1962, the Dez Dam on the Dez River was designed to irrigate the Khuzestan plain and to
supply electricity to the province (U.S.Library of Congress, 1987). After several years of
operation, the dam had achieved only a small part of its goals, and the government decided
that the lands below the dam and other dams nearing completion required special
administration. As a consequence, a law was passed in 1969 nationalizing irrigable lands
downstream from dams. The lands below the Dez Dam were later leased to newly establish
domestic and foreign companies that became known as agribusinesses (U.S.Library of
Congress, 1987).
A sound foundation is one of the fundamental necessities in dam construction and critical
geological phenomena have caused many problems in large dams.
One of the problems with regards to foundations is that water, due to high foundation
permeability is lost through seepage, which is the case in the Asmari Formation in southwest
Iran. Seepage depends on various parameters, such as foundation materials, geological and
structural conditions of the area and also the hydraulic characteristics of the dam foundation.
Due to complex local conditions, the need for more widespread and logical insight into the
geology has increased and with it also to ensure the need for more extensive engineering and
geological investigations of safety and stability, during the dam life. The permeability and
porosity are important especially regarding the grouting and the assessment of the influence of
weathering on foundation rocks also plays an important role.
Another common geological problem is overtopping due to a landslide in the reservoir that
produce a tsunami which can rapidly wear away the land on either side of the dam (Hawker,
2000).
Thandaweswara (2012) listed dam failures depending on the type of dam and the causes of
failure are classified as follows:
I.
II.
III.
IV.
Hydraulic failures;
Piping and seepage through foundation and body of dam;
Overtopping and
Stresses developed within the structure.
A study of dam failures in the world has indicated 40 percent of dam breaks are related to
geological problems (Thandaweswara, 2012).
The following are some case histories regarding geological problems that caused failure and
serious problems in dam construction;
a) Malpasset arch dam (France) was breached in 1959 due to a fault that was later found
to be the cause of the disaster. The dam completely collapsed and produced an
enormous dam break wave, or wall of water, 40 m high and moving 70 km per hour,
destroying two villages and killing 450 people in the resulting flood (Bellier, 1967).
2
b) Vajont arch dam (Italy), one of the tallest dams (262 m) in the world caused
overtopping of the dam in 1963 due to a landslide in the reservoir. This flood wave
caused the deaths of 2000 people (Semenza, 1965).
c) St. Francis dam with a curved concrete gravity wall failed disastrously on its first full
impoundment in 1928 killing about 450 people in the San Francisquito and Santa
Clara River valleys because of unknown palaeo mega-slides on the left bank within
the Pelona Schists. It was the biggest American civil engineering neglect in the
twentieth century (Rogers, 1995).
d) Teton rockfill dam in the United States failed in 1976. Investigations into the cause
placed blame on the permeable soil used in the core and on fissured rhyolite in the
foundation that allowed water to seep under the dam (Arthur, 1977).
e) Keban a composite dam was built in 1974 on the Euphrates River in Turkey. The
rockfill and concrete gravity structure rests on karstic marble and limestone. A crab
cavity with a volume of 104 000 m3 was detected during the construction in the
foundation on the left flank (Ozbek, 1975).
f) Hales Bar dam was constructed on the Tennessee River on 1913. The Tennessee
Valley Authority (TVA) spent two decades unsuccessful trying to fix a leakage
problem in the foundation. Finally the TVA decided to replace the dam by building
Nickajack Dam about 10 km downstream in 1968 (Tennessee Valley Authority,
1972).
g) Lar rockfill dam was built in 1981on a heavily faulted and fractured region of
Damavand volcano region in the north of Iran. The fracturing increased the
development of karst and sinkholes in the limestone below the dam in addition the
acidic solutions that originated from the volcano accelerated the process of dissolution
and development of karstic zones. The grouting operations continue for several
decades and was unsuccessful untill recently (Uromeihy, 1999).
The responsibility of a geological engineer is to select the best dam location (site selection)
and to give proper solutions for geological problems. By using technical information from
different dam construction projects in the Zagros Range situated in the southwest of Iran, it
has been attempted in this research, to evaluate the geological characteristics of the rock mass
on dam site location for the construction of the dams (Koleini, 1997).
In general, the large dams and power plants that are situated in southwest Iran are on
limestone, dolomitic limestone, marly limestone and marlstone belonging to the OligoMiocene rocks of the Asmari Formation and the engineering geological studies associated
with the location of these dams present new engineering geological information on the Asmari
Formation limestone of south-western Iran.
3
38
Turkey
40
Caspian Sea
Turkmenistan
Sefid
Atrak
Qezelowzan
Kashaf Rud
36
Tehran
Qom
Ilam
34
Seymareh
Isfahan
Se
Afghanistan
Karun
32
Karkheh
Iraq
K-3 Zayandeh
K-4
Marun
M
30
Zohreh
Kerman
Shiraz
Zahedan
Dalaki
Pakistan
Sa
ia
rs
Pe
28
Ghareh aga haj
n
Saudi Arabia
0
f
ul
24
G
26
Oman Sea
50 100 km
45
50
55
60
65
Figure 1.1. The map indicates some major rivers in Iran and dam localities in the Zagros region
(research area). Salman Farsi dam (Sa), Marun dam (M), Karun-4 dam (K4), Karun-3 dam (K3),
Seymareh dam (Se).
1.1.1. Aims of Thesis
The dam construction projects that are considered in this research include the following:
1. Karun-3 Dam (K-3) and power plant (constructed) on the Karun River - about 28 km
east of Izeh town at Khuzestan Province.
2. Karun-4 Dam (K-4) and power plant (under construction) on the Karun River -35 km
west to southwest Lordegan town, 85 km southwest of Shahrekord City in Chahar
Mahal Bakhtyari province.
3. Marun Dam (M) and power plant (constructed) on the Marun River-about 19 km
northeast Behbahan City in Khuzestan Province.
4. Seymareh Dam (Se) and power plant (under construction) on the Seymareh River
about 106 km southeast of Ilam City in Ilam Province.
5. Salman Farsi (Sa) or Ghir Dam and power plant (under construction) on the GharehAghaj River, about 140 km south of Shiraz City and 12 km north-east of Ghir in the
Fars Province.
The aims and purpose of this research are the following:
1

a)
b)
c)
d)
e)
f)
g)
h)
i)
j)

Investigate the engineering geological characteristics of the (Asmari) rock mass at the
various construction sites including:
Determination of geological characteristics of dam locations.
Preparation of lithological columns and engineering geological sections along the dam
axes.
Preparation of thin sections of rock samples for petrographical analysis.
Identification of hydrogeological characteristics of the dam locations, particularly
porosity and permeability- also resultant grouting that will be needed at each site.
Characteristics and determination of rock mass classification along tunnels and slopes
and the investigation of their stabilities by means of ordinary experimental method
classifications.
Introduction of stabilization measures for tunnels and slopes.
Determination of net allowable pressure and cuttability classification of the Asmari
Formation limestone.
Joint study (discontinuity survey).
Exposed foundation maps at each dam site.
Use of site bedrock as construction material in dams.
Introduce an engineering geological model (rock material and rock mass properties
and characteristics) for the Asmari Formation in the Zagros Region.
1.1.2. Previous Work
The name Asmari Formation was introduced by Busk and Mayo (1918) and referred to a
sedimentary sequence of Cretaceous-Eocene age. The Asmari Formation was also
stratigraphically studied by Richardson (1924), Van Boecha, Lees et.al (1929). Lee (1933)
revised the previous work and considered the Asmari Formation to be of Oligo-Miocene age.
The formation was studied in detail stratgraphically and formally defined by James and Wynd
(1965). Adams and Bourgeois (1965) revised the biostratigraphy of the Formation in southwestern Iran and various authors also discussed the Asmari Formation: Wells (1967), Sisler
(1971), McCord (1974), Stonly (1975), Kalantari (1986, 1992) and Jalali (1987), National
Iranian Oil Company (NIOC), Zahedinejhad, (1987), Seyrafian et al., (1996, 1998, 2002),
Kimiagari, Vazirimoghadam and Taheri (2005).
All of the above concentrated basically on the stratigraphy of the Asmari Formation in the
Zagros region.
The engineering geological reports on the Asmari Formation are from the:
Engineering geological investigations of various dam sites, located on the Asmari Formation
in the south-western Iran, by Mahab Ghodss Consulting Engineers Company (MG. co.) dated
1984, 1986, 1993, 1996, 2003 (Ministry of Energy- Iran).
1.2. Geography of Iran
Iran is situated in Southwest Asia, bordering the Gulf of Oman, the Persian Gulf (southern
border), and the Caspian Sea, Armenia, Azerbaijan, Turkmenistan (northern border), Iraq,
Turkey (western border) and Pakistan, Afghanistan (eastern border) between latitudes 25° and
39° north and longitudes 45°and 61° east. Iran is one of the world's most mountainous
countries with high contrasting green oases (Figure 1.2).
With an area of 1 648 000 km2, Iran ranks sixteenth in size among the countries of the world.
Iran is about one-fifth the size of the continental United States, or larger than the combined
area of the contiguous states of California, Arizona, Nevada, Oregon, Washington, and Idaho.
5
Iran's diagonal distance from Azerbaijan in the northwest to Baluchestan Sistan in the
southeast is approximately 2 333 km (U.S.Library of Congress, 1987).
1.2.1. Topography
Iran (Persia) consists of rugged mountainous rims surrounding high interior basins. The
main mountain chain is the Zagros Mountains comprising a series of parallel ridges
interspersed with plains that bisect the country from northwest to southeast (Figure 1.2).
Many peaks in the Zagros exceed 3 000 m above sea level, and in the south-central region of
the country, there are at least five peaks that are over 4 000 m. As the Zagros continue into
southeastern Iran, the average elevation of the peaks declines dramatically to under 1500 m
(U.S.Library of Congress, 1987).
The narrow but high Alborz Mountains rim the Caspian Sea. Volcanic Mount Damavand
(5 600 m), located in the centre of the Alborz range, is not only the country's highest peak but
also the highest mountain on the Eurasian landmass west of the Hindu Kush.
Figure 1.2. The topographic map of Iran (Iran topo en.jpg, 2006).
The Alborz represents a north branch of the Alpine-Himalayan orogenic system and runs
for a distance of 960 km separating the Caspian Lowland from the Central Iran Plateau. The
centre of Iran consists of several closed basins that are collectively referred to as the Central
Plateau. The average elevation of this plateau is about 900 m, but several of the mountains
that tower over the plateau exceed 3 000 m. The eastern part of the plateau is covered by two
6
salt deserts, the Dasht-e Kavir (Namak) and the Dasht-e Lut. Except for some scattered oases,
these deserts are uninhabited (U.S.Library of Congress, 1987).
The two mountain ranges of Iran provide for a variety of climates, though most of Iran is
dry. Of the small rivers and streams, the only one that is navigable is the Karun, which
shallow-draft boats can negotiate from Khorramshahr to Ahwaz, a distance of about 180
kilometres. Several other permanent rivers and streams also drain into the Persian Gulf, while
a number of small rivers that originate in the northwestern Zagros or Alborz drain into the
Caspian Sea. On the Central Plateau, numerous rivers, most of which have dry beds for the
greater part of the year, form from snow melting in the mountains during the spring and flow
through permanent channels, draining eventually into salt lakes that also tend to dry up during
the summer months (U.S.Library of Congress, 1987).
1.2.2. Climate and Water Resources
The climate of Iran is one of great extremes due to its geographic location and varied
topography. The summer is extremely hot with temperatures in the interior rising possibly
higher than anywhere else in the world; certainly over 55°C has been recorded. In winter,
however, the great altitude of much of the country and its continental situation result in far
lower temperatures than one would expect to find in a country in such low latitudes.
Tempratures of - 30°C can be recorded in the north-west and - 20°C is common in many
places such as west and centre (U.S.Library of Congress, 1987).
Iran can be divided into the following major river basins: the Central Plateau in the middle,
the Lake Urumiyeh basin in the northwest, the Persian Gulf and the Gulf of Oman in the
south-southwest, Lake Hamoun basin in the east, Kara-Kum basin in the northwest and the
Caspian Sea basin in the north. (Ministry of Energy, 1992).
The rainfall characteristics of the above basins are summarized in Table 1.1.
All of these basins, except the Persian Gulf and Gulf of Oman, are interior basins. The
Karun River, with a total length of 890 km, occurs in the southwest of the country. The few
streams that empty into the Central Plateau dissipate into the saline marshes. All streams are
seasonal and variable with spring floods causing enormous damage, while there is little water
flow in summer when most streams disappear. Water is however stored naturally
underground, finding its outlet in subterranean water canals (qanats) and springs and is also
tapped by wells (Ministry of Energy, 1992).
Table 1.1. Rainfall in the major basins in Iran (Bureau of Operation and Maintenance of Dams and Irrigation
Networks, 1995).
Basin
Central Plateau
Persian Gulf and Gulf of Oman
Caspian Sea
Lake Hamoun and Kara-Kum
Lake Urumiyeh
Total
Total area (km²)
832 000
As % of total area
51
Rainfall (mm/y)
165
Rainfall (km/y)
138
As % of total rainfall
33
431 000
178 000
26
11
366
430
158
77
150 000
57 000
1 648 000
9
3
100
142
370
252
21
21
415
38
19
5
5
100
Internal renewable water resources are estimated at 128.5 km3/year. Surface runoff
represents a total of 97.3 km3/year, of which 5.4 km3/year comes from drainage of the
aquifers, and groundwater recharge is estimated at about 49.3 km3/year, of which 12.7
km3/year is obtained from infiltration in riverbeds. Iran receives 6.7 km3/year of surface
water from Pakistan and some water from Afghanistan through the Helmand River. The flow
of the Arax River, at the border with Azerbaijan, is estimated at 4.63 km3/year. The surface
runoff to the sea and to other countries is estimated at 55.9 km3/year. The total safe yield of
7
groundwater (including non-renewable water or unknown groundwater inflow from other
countries) has been estimated at 49.3 km³/year (Ministry of Energy, 1992).
The Zagros serves as the main origin of the rivers running into the Persian Gulf and Oman
sea watersheds. Among all these rivers, the major ones are: Arvand Rud, Gamasb, Karun,
Rajah, Zaal and Marun join and form Jarahi, Seymareh, Qareh Aqhaj, Zohreh, Dalaki,
Mend, Shur, Minab, Mehran and Naband (Figure 1.1).
The major rivers running into the Caspian Sea (north) from Iranian shorelines flow from the
northern Alborz attitudes like: Aras, Sefid Rud, Chalus, Haraz, Sehezar, Babol, Talar, Tajan,
Gorgan, Atrak, Qarasu and Neka. Zayandeh Rud flow through central Iran. Halil Rud and
Bampur occur in the southeast of Iran (Ministry of Energy, 1992).
1.3. Geology of Iran
1.3.1. Structural Units
Fundamental differences in crustal character and in age of basement consolidation allow
three major structural units to be distinguished, separated from each other by an ophiolitebearing suture. Other criteria such as structural style, age and intensity of deformation, age
and nature of magmatism, are used to subdivide these major zones into smaller elements
(Figure 1.3). The three major units and their main constituents (Berberian and King, 1961) are
as follows:
1. A crystalline basement consolidated during the Precambrian and a platform-type
Palaeozoic development forms the basement of the Zagros Fold Belt.
2. The central unit is interpreted as an assemblage of marginal Gondwana fragments
that were united with the mother-continent and separated from the northern (Eurasian)
continent in the Palaeozoic, but detached from Gondwana and attached to Eurasia in
the Mesozoic, and finally rejoined by Gondwanic Afro-Arabia in the Late Cretaceous.
It comprises Central Iran and the Alborz.
3. The northern unit is sharply separated from the central unit by the north Iran Suture. It
is characterized by continental crust including remnants of more or less cratonized
former (Palaeozoic) oceanic crust that seems to reflect a Palaeotethys. This northern
unit represents a marginal strip of the Hercynian realm of Central Asia-broadly
overlapped by the Alpine realm. It was deformed and largely consolidated by strong
early Kimmeridjian folding and a Late Alpine folding (Stocklin, 1977). The northern
unit comprises the South Caspian Depression and the Kopet Dagh Range.
1.3.1.1. Zagros
In the simply folded belt of the Zagros Mountains, a sequence of Precambrian to Pliocene
shelf sediments about 8-10 km thick has undergone folding from Miocene to Recent. The
Zagros Mountains trend southeast through northeast Iraq to southwest Iran. They are the
topographic expression of an orogenic event that continues to the present time. The
sediments have been folded into a series of huge anticlines and synclines. The folding has
taken place since the Miocene and is reflected in the topography, which is dominated by
anticlinal mountains and synclinal valleys. The anticlinal oil traps of Iran and northeast Iraq
are in this belt. The Zagros Orogenic Belt is bounded to the southwest by the stable platform
of Arabia, where shelf sediments laterally equivalent to those in the simply folded belt are
8
virtually undeformed and overlie the metamorphic rocks of the Arabian Shield (Geological
Survey of Iran, 2006).
SS
0
75
150
UB
225 Km
Figure 1.3. The main structural units of Iran (after Berberian and King, 1961).
1.3.1.2. Zagros Thrust Zone
The folded belt passes northeastward without a sharp boundary into a narrow zone of
thrusting bounded on the northeast by the main Zagros Thrust line (Figure1.3). In this zone,
older Mesozoic rocks and the Palaeozoic platform cover were thrust southwestward in several
schuppen-like slices on the younger Mesozoic and Tertiary rocks of the folded belt. The thrust
zone represents the deepest part of the Zagros Basin in Mesozoic and early Tertiary time
(Geological Survey of Iran, 2006).
1.3.1.3. Sanandaj – Sirjan Metamorphic Belt (SS)
The Sanandaj-Sirjan Zone was first recognized as a separate linear structural element by
Stocklin (1968). The zone lies between the main Zagros Thrust in the southwest and the
Urumiyeh-Bazman volcanic belt in the northeast. The ranges occupy a northwest trending belt
in which the Zagros structural grain is overprinted on the typical Central Iran structural
framework. Characteristic features include the consistent Zagros trend of the zone as a whole,
the nearly complete lack of Tertiary volcanics and the poor development of Tertiary
formations in general. Part of the zone is characterized by Palaeozoic volcanism and
Hercynian or Early Kimmeridjian metamorphism (Geological Survey of Iran, 2006).
9
1.3.1.4. Urumiyeh–Bazman Volcanic Belt (UB)
This volcanic belt runs parallel to the Sanandaj-Sirjan Zone to the northeast, and owes its
existence to the widespread and intensive volcanic activity, which developed on the Iranian
plate from the Upper Cretaceous to Recent time. The Urumiyeh-Bazman volcanic belt is
supposed to have resulted from the collision of the Arabian and Central Iranian continental
plate margins. It is represented by sub-alkaline volcanics that vary in composition from
basaltic through andesitic to rhyolitic composition (Geological Survey of Iran, 2006)
1.3.1.5. Central –East Iran Micro Plate
Central Iran, in a broad sense, comprises the whole area between the north and south
Iranian ranges. Within the Iranian plate the central east Iran microplate is bordered by the
Great Kavir Fault in the north by the Nain-Baft Fault in the west and southwest and by the
Harirud Fault in the east. It is surrounded by the Upper Cretaceous to Lower Eocene
ophiolite and ophiolitic melange. The microplate consists of different structural components;
the Lut Block, Kerman-Tabas Block, Yazd Block and Anarak-Khur Bloc (Geological Survey
of Iran, 2006).
1.3.1.6. Makran and Zabol –Baluch Zone, Southeast Iran
Makran and Zabol-Baluch in the southeast of Iran are post-Cretaceous flysch-molasse
belts, which join together in southeast Iran and continue to the Pakistan Baluchestan Range.
The flysch sediments were deposited on the Upper Cretaceous ophiolites (Geological Survey
of Iran, 2006).
1.3.1.7. Alborz
The Alborz Mountains form a gently sinuous east-west range across northern Iran south of
the Caspian Sea, and constitute the northern part of the Alpine-Himalayan Orogeny in western
Asia. The Alborz Range in north Iran is stratigraphically and structurally related to Central
Iran (Geological Survey of Iran, 2006).
1.3.1.8. Kopet-Dagh
The northeast active fold belt of Iran, the Kopet Dagh, is formed on the Hercynian
metamorphosed basement on the south-western margin of the Turan Platform. The belt is
composed of about 10 km of Mesozoic and Tertiary sediments (mostly carbonates) and, like
the Zagros, was folded into long linear northwest-southeast trending folds during the last
phase of the Alpine Orogen, in Plio-Pleistocene time (Geological Survey of Iran, 2006).
1.3.2. Stratigraphy of Iran
1.3.2.1. Precambrian Basement
The consolidation of the Iranian basement by metamorphism, partial granitization and
partly by intense folding took place in the Late Precambrian (Figure 1.4). This event has been
attributed to the 'Baikalian' or Pan-African Orogeny. Isotopic data of Iranian basement rocks
give ages between 600 and 1 100 Ma (Geological Survey of Iran, 2006).
41
A similar range of isotopic data has been obtained for Arabian Shield rocks. An important
post-Pan-African magmatism is documented by the widespread Doran Granite, which cuts the
Upper Precambrian rocks and is covered by Lower Cambrian sediments. Late Precambrian
postorogenic volcanics, mainly alkali rhyolite, rhyolite tuff and basic dykes are known in the
Eocambrian formations. The basement is exposed only in limited parts of the platform area. It
consists of low-grade (greenschist facies) metamorphosed, fine-caustic sediments (Geological
Survey of Iran, 2006).
1.3.2.2. Palaeozoic Platform
The platform deposits are well developed in the main and south Alborz Range, in the
greater part of central and east Iran as well as in southwest Iran. The north Iran Suture marks
the northern termination of the platform regime of the Arabian-Iranian Plate. The Pan-African
Orogeny in Iran was followed by a long period of tectonic calm during most of the interval
from the Infracambrian to the middle Triassic (Geological Survey of Iran, 2006).
The rock sequence deposited during this time displays all the characteristics of a platform
cover. It indicates an epicontinental environment with alternating shallow-marine, lagoonal
and continental deposits (Figure 1.4). The thickness of the whole sequence is between 3 000
m and 4 000 m and increases up to 8 000 m in the region of Tabas in east Iran (Stocklin,
1965; Ruttner et al., 1968).
1.3.2.2.1. Precambrian–Cambrian Boundary
The Precambrian-Cambrian boundary is now known from many places in Iran, notably in
Alborz, near Kerman. The Lower Dolomite Member of the Soltanieh Formation contains an
assemblage of phosphatic tubes and other poorly preserved remains. The succeeding Lower
Shale Member bears macroscopic algae (Hamdi et al., 1989).
1.3.2.2.2. Infracambrian –Ordovician
Infracambrian rock units in Iran were deposited over large areas after the Pan-African
tectonic phase. These movements gently folded and uplifted Precambrian fine clastic, flyschtype sediments (Kahar Formation, Morad Series and Shorm Beds) along Pan-African trends
and caused epeirogenic uplifting, and emergence of lowland areas in west Iran, in east Central
Iran and probably also in East Iran. In central Iran and northwest Iran, the Eocambrian rock
units are mainly shallow water shelf platform carbonates, which interfinger towards the
northern Iran Suture with brown, fine-grained sandstone-shale sequences defined as the
Bayandor Formation. The carbonates are stromatolitic dolomites of the lower parts of the
Soltanieh Formation (Geological Survey of Iran, 2006).
1.3.2.2.3. Silurian to Lower Devonian
Early Caledonian tectonic movements resulted in an uplifting of west and south Iran and
caused emergence of the southern Caspian and central Alborz area, which were temporarily
linked to the west Iranian land platform. The pre-Zagros swell emerged with a large low land
area in southwest Iran and remained free of marine ingressions in Silurian-early Devonian
time. Central and northwest Central Iran was depositional areas in the Silurian-early Devonian
time. In east central Iran, basalts are at the base of the Niur Formation, a predominantly
shallow water platform limestone and dolomite sequence (Weddige, 1984). This marine
fossiliferous facies, which laterally interfingers with fine clastics and sandstones, is only
44
developed in east central Iran to a thickness of about 500 m (Geological Survey of Iran,
2006).
1.3.2.2.4. Middle Devonian to Carboniferous
1.3.2.2.4.1. Alborz
Marine deposits of Devonian age are known in the Maku area (northwest Iran). They
consist of dolomite with some intercalations of sandstone and quartzite and are called the
Muli Formation (Alavi Naini and Bolourchi, 1973). The thickness of the Muli Formation is 1
250 m and metamorphic rocks unconformably underlie it. In central Alborz, the Upper
Palaeozoic sedimentary cycle began with the transgression of the sandy Jeirud Formation
(Upper Devonian). The Guired Formation consists in its lower part of sandstone, shale, sandy
limestones and several phosphatic layers, followed by sandstones (Alavi Naini and Bolourchi,
1973). Lower Carboniferous of Central Alborz is made up of dark Limestone with
subordinate marl intercalations in the lower part (Mobark Formation). Formation is about 450
m thick and disconformably overlies the Jeirud Formation. In east Alborz the Khosh Yelagh
Formation transgressed with a basal conglomerate on the Padeha Formation. The Khosh
Yelagh Formation consists of shale, limestone, sandstone and basic volcanics (Geological
Survey of Iran, 2006).
1.3.2.2.4.2. Central Iran
In east Central Iran the cycle of middle Devonian to late Carboniferous marine sediments
reaches a thickness of 1 500 to 2 000 m and was defined as the Ozbak Kuh Group (Ruttner,
Nabavi and Hajian, 1968; Stocklin, Eftekharnezhad and-Hushmandzadeh, 1965). It consists of
the Sibzar Dolomite at the base (100 m thick), the Bahram Formation (300-500 m thick of late
Devonian age) and the Shishtu Formation (300-400 m thick, of alternating marls, shale and
limestone of the late Devonian to early carboniferous age); the cycle terminates with the
Sardar Formation (shales, sandstones and sandy limestone) of the late Visean to late
Carboniferous age (Geological Survey of Iran, 2006).
1.3.2.2.4.3. Zagros Area
The Devonian is nowhere present in the southwest of Iran. The Carboniferous sandstone is
very consistent, being present beneath the Permian limestone wherever the base of this
limestone is exposed (Setudehnia, 1972). This Carboniferous sandstone is disconformably
underlain by Cambrian sediments in the Kuh-e-Dinar, Zard–Kuh and Oshtoran–Kuh areas.
Ordovician and Silurian sediments in the Kuh-e-Surmeh and Gahkum-Faraghan areas also
disconformably underlie it respectively. The upper boundary of the Carboniferous with the
Permian is not clear. These two units are often combined and referred to as PermoCarboniferous (Geological Survey of Iran, 2006).
1.3.2.2.5. Permian Sedimentary Cycle
Over wide areas in northwest Iran and in the main Alborz Range, a red-clastic shallow
marine transgressive phase, the Dorud Formation, indicates Permian sedimentation. The
Dorud Formation interfingers towards the eastern Alborz with shelf carbonates and towards
central Iran it changes into a thinner, basal quartz sandstone member (Geological Survey of
Iran, 2006).
42
1.3.2.2.6. Permian –Triassic Boundary
The lowermost Triassic, as well as a continuous section between the Permian and Triassic,
is so far only known from Julfa (northwest Iran) and Abadeh (west central Iran). At Julfa the
dark, brachiopod-bearing limestone of Guadalupian age is conformably overlain by 33 m of
shales, marls and thin limestones of whitish gray and purple color; these are the Julfa Beds
(Stepanov et al, 1969), which contain a peculiar Late Permian fauna and correlate in minute
detail with the stratotype of the Dzhulfian (Geological Survey of Iran, 2006).
1.3.2.3. Mesozoic
In the geological history of Iran, the Mesozoic Era is of greater significance, since many
important geological events occurred during this era. The tectonic and palaeogeographic
evolution of Iran during the Mesozoic was controlled by the geodynamic interaction of the
Eurasian continental margin and the Tethyan oceanic belt (Geological Survey of Iran, 2006).
1.3.2.3.1. Lower and Middle Triassic Sedimentary Cycle
The cycle of platform sedimentation began with the Permian transgression, continued into
the Triassic and ended in late Middle Triassic. The Lower and Middle Triassic facies on the
Iranian and on the Turanian Plates are significantly different. In contrast to the carbonate
platform sedimentation on the Iranian Plate, geosynclinal sediments were deposited on the
southern part of the Turan Plate (east Kopet Dagh and south Caspian area) and in the Nakhlak
area in Central Iran. This Triassic facies has the following characteristics; besides the
carbonate rocks, the sequence consists of marine and non-marine clastic sediments and
volcanic rocks (tuff and lava) are abundant; the thickness of the sequence reaches 1 000-3 000
m indicating strong subsidence of the basin. In Iran this facies type appears only in few
localities such as Aghdarband in east Kopet Dagh (Ruttner, 1993), in Talesh area in the west
Alborz (Davies et al., 1972) and at Nakhlak north of Anarak in Central Iran (Davoudzadeh
and Seyedemami, 1972).
The Zagros depositional area was separated from the central Iran realm by the opening of
Neotethys in Late Palaeozoic or in Early Triassic time. The Zagros Triassic epicontinental
basin was filled with carbonates, evaporites and the Dashtak basal red shale of Khaneh Kat
Formation. The thickness of the Khaneh Kat Formation is 400 m or more (James and Wynd,
1965).
1.3.2.3.2. Upper Triassic to Middle Jurassic Sedimentary Cycle
The time interval from Late Triassic to Middle Jurassic was in fact a cycle of
sedimentation between two tectonic events of the Early Kimmerian movements and the midJurassic event. As a result of the Early Kimmerian tectonics, most parts of Iran were split into
a horst and graben mosaic. Synsedimentary fault tectonics caused the formation of troughs
that developed during the deposition of the Shemshak Formation in central and east Alborz
and in north Kerman (Geological Survey of Iran, 2006). During the Late Triassic to Middle
Jurassic, these troughs were filled with 3 000- 4 000 m of sediments. These basins were
temporarily connected with the open shallow part of the Tethys. The alternation of
subcontinental coal-bearing facies with plant remains and marine carbonates in the sequences
indicate four transgressive–regressive macro cycles. They are represented accordingly by
Upper Triassic, Lower, Middle and Upper Jurassic sediments (Geological Survey of Iran,
2006).
43
Seymareh
Karun-3
Karun-4
Marun
Salman Farsi
0
110 220
330 Km
Figure 1.4. Geological map of Iran, SSZ represent the Sanandaj-Sirjan Zone (after Pollastro et al., 1997). The
dam localities in Zagros region are presented by red triangle.
1.3.2.3.3. Middle and Upper Cretaceous
The Late Kimmerian and early Alpine relief were peneplaned and partly covered by red
clastic debris. In the Barremmian and Aptian a shallow sea transgressed extensively over
almost the whole of Iranian territory and uniform Orbitolina Limestone was deposited
everywhere. Some higher areas in east Iran, on the Lut Block, Shotori Horst and west of
Kerman remained emerged or else were stripped again after the Austrian movements
(Cenomanian-Turonian) (Geological Survey of Iran, 2006).
Turonian and Coniacian sediments are missing in many parts of northern and central Iran. In
north central and east Alborz the Cretaceous sediments mainly represent deep shelf and neritic
facies. Southwest and south Iran were not much affected by the early Alpine movements and
remained as an epicontinental sea. A slight regression is only indicated by the Late JurassicEarly Neocomian evaporites towards the Arabian Platform (Geological Survey of Iran, 2006).
The Albian to Cenomanian rock units of the Zagros area are represented by the Bangestan
Group. During this period, the massive, neritic wackestones and packstones of the Sarvak
Formation were spread over Kajhdomi. A pelagic facies indicating deeper water is developed
41
in the eastern Interior Fars and along a furrow, extending from northeastern Fars through the
Bakhtyari to central Lorestan (James and Wynd, 1965).
1.3.2.4. Tertiary
Regional folding in Late Cretaceous-Palaeocene time produced a regional unconformity at
the base of the Tertiary throughout the greater part of north central and eastern Iran. Marine
areas remined in Palaeocene time in flysch troughs and subsiding shelf areas in east Iran, in
landward Makran (southeast Iran), in parts of the Urumiyeh-Hamadan Zone and in the Zagros
Miogeosyncline (Geological Survey of Iran, 2006).
1.3.2.4.1. Palaeogene (excluding Upper Oligocene)
In the northern Alborz area, middle Alpine movements caused emersion only in late
Palaeocene time. Here Maastrichtian-Danian marine-neritic sedimentation continued into the
Palaeocene. In the Kopetdagh (northeastern Iran), the middle Alpine movements caused
regression, and red beds and lagoonal deposition of the Pestehligh Formation were deposited
in Early Palaeocene time (Afshar-Harb, 1979). Shortly afterwards during the Upper
Palaeocene, the Kopet Dagh Foredeep extended to the south and marine shelf conditions
returned, where the Chehel Kaman Limestone (300 m to 400 m thick) was deposited
Davoudzadeh, 1969). The northern part of the Alborz and the southern Caspian coastal areas
remained a landmass, throughout the Eocene. This land area was fringed by reefal limestones
in the westernTalesh (southwestern Caspian area) through most of the Eocene and by lagoonal
evaporite deposits in the west-central Alborz area during the Early Eocene time.
During the Lutetian stage, flysch troughs continued to subside along the zone between
Zagros and Central Iran, along the Great Kavir Fault, in the east Iranian Baluch and landward
Makran Range and along the Hamadan-Urumiyeh Zone. In the area N of Nain, more than 3
000 m of Middle Eocene fine-clastic flysch sediments( Akhoreh Formation) were
accumulated with a fauna of Nummulites partschi and N. burdigaleinsis (Davoudzadeh,
1969).
1.3.2.4.2. Upper Oligocene to Lower Miocene
Northern Iran was already separated from central and north-western Iran by the rising Qara
Dagh (northwest Iran), Alborz and Kopet Dagh ranges. Eastern Iran was essentially a
continental area, with temporary brackish and marine embayments only along the eastern
Alborz Foredeep and in the Jazmurian Depression (southeast Iran). The Qom Sea in central
and northwest Iran and the Asmari Sea in southern and south-western Iran may have been
connected by sea lanes in the Kermanshah area and possibly in north Kurdistan. Temporary
sea connections may have also existed between the Oligocene Makran Flysch trough in
southeastern Iran and the Jazmurian Platform, but evidence of these channels was eroded in
late Alpine thrusting and uplifting of the Zagros and Zendan (southeastern Iran) ranges
(Geological Survey of Iran, 2006).
The Qom Sea started to cover north-western and central Iran from the southwest during
Middle Oligocene time. The north and east shorelines up to the foot of the Alborz Range and
to the east of the Dasht-e-Kavir were reached by the sea only in early Miocene time. Starting
with a basal sandy calcarenite, with reworked Eocene volcanic pebbles, the marine area was
somewhat irregularly covered in three cycles of marl, limestone and evaporite deposition in
thickness up to 1 500 m (Geological Survey of Iran, 2006).
45
Shallow-water bioclastic and reef detrital yellow-cream weathered limestones 100 to 250
m thick (in some areas increasing to 500 m) uniformly cover the platform areas on the
northeast side of the Zagros Range, in the Esfahan-Sirjan Depression, at the foot of the Alborz
Range and on shoal areas inside the Central Basin, which were only later flooded by the sea.
Some more basinal areas are filled with dark, partly bituminous marls and shales (Sarajeh and
Talkheh anticlines 100 km south of Tehran) of thickness 750 to 1 000 m. The fauna in the
lower part of the Qom Formation indicate Chattian to lower Aquitanian stages (Huber, 1979).
The bryozoan's limestones, marls, shales and anhydrite of the middle part contain fauna of the
late Aquitanian Stage. The upper part of the Qom Formation is of Burdigalian age and can
reach 500 m in thickness. This cycle is terminated by regression and deposition of anhydrite
and salt of Lower Miocene upper evaporite (Geological Survey of Iran, 2006).
In the South Caspian area, The Neogene rock units start only in Vindobonian time with the
deposition of red beds on eroded Palaeocene and Upper Cretaceous strata. These
Vindobonian-Sarmatian units have thickness ranging from 600 to 800 m in the exposures of
the Mazanderan foothills. In the East Mazanderan embayment, they give way to clastic
continental beds, which also cover the marine sequence of the Mazanderan plain, nearly 2000
m thick. Towards the Caspian Sea, the continental beds interfinger with fine-clastic marine
Pliocene rock units and rapidly increase in thickness to more than 3 000 m. In the Gorgan
embayment, this part of the Neogene's sequence is represented by brown clays, marls and
siltstones of the Chelecken Formation (Geological Survey of Iran, 2006).
In the Kopet Dagh, the intermountain valleys of the Atrak and Kashafrud were filled with
partly coarse clastics and contain chalk and freshwater limestones of temporary lakes. In the
northern Kopet Dagh foredeep, the Neogene clastic sequence has more than 2000 m thickness
in the Darreh Gaz area. No marine Neogene units are recorded in the central and east Iranian
Kopet Dagh (Geological Survey of Iran, 2006).
1.3.2.4.3. Neogene Basin
1.3.2.4.3.1. Central Iran
With dimensions of 700 km west to east and 500 km from north to south, the Central Basin
covers the Great Kavir Desert and Draya-e-Namak Playa and has an irregular triangle shape.
It covers an area of more than 150 000 km. In the eastern part, basal red beds and
conglomerates of a continental red-bed sequence may be partly time equivalents of the Qom
Formation. To the north, the Central Basin is limited by the Central Alborz Range and to the
southwest by the Urumiyeh-Bazman volcanic range. The coarse clastics of these marginal
troughs interfinger basin ward with mudstones and evaporites. Great thicknesses (more than
600 m) of these softer more mobile sediments were recorded in the northern Kavir area and in
the southern Siah Kuh and Qom-Saveh area, whereas the more stable, incipient horst areas of
Eocene volcanic rocks were covered only with 1 000-2 000 m of Neogene clastics. In the
interior part of the Central Basin, the Neogene sequence starts with evaporites (upper
evaporites), because they cover and seal the Qom limestone reservoir in the Qom and Semnan
areas (Huber, 1979). This first evaporite cycle has a thickness of up to 800 m and consists of
rock salt, soft red salt-clay, green shale and gypsum beds in several repeated cycles. Some
papery weathering bituminous calcareous shale (50 cm thick) is also interbedded and
terminates the cyclothems (Geological Survey of Iran, 2006).
The bulk of the Upper Red formation is formed by thickly bedded gray–brown calcareous
sandstones and red-brown mudstones with few intercalations of thin, fetid pyritic limestones
lenses and green shale beds of playa and mudflat type containing ostracods and occasionally
46
miliolids and gastropods. This part has a thickness of 2 000-4 000 m (Geological Survey of
Iran, 2006).
1.3.2.4.3.2. Lut Basin
With dimensions of 400 km north-south and 200 km east-west, the Lut Basin subsided in
the late middle Alpine tectonic phase on a basement of Eocene andesitic lava flows, mainly
along the western Lut (Nayband-Lakar Kuh) and eastern Lut fault systems. The northern part
of the Lut Block was covered by several andesitic, dacitic and rhyolitic lava flows, which
poured out partly from fissure volcanoes along tensional faults, and were partly spread,
together with tuffs and ashes, from eruption centres, which were later plugged by porphyry
masses, while the central Lut was covered by silt and salty mud sheets of a few hundred
metres thick. The marginal trough zones along the western and eastern Lut fault system were
filled with several thousand metres of red beds and conglomerates mainly in two cycles of
deposition, separated by a late Alpine unconformity.
The Lut Formation (Bobek, 1969) comprises the loess-like deposition, which has been shaped
into the fantastic Lut towns (by wind erosion): smaller erosional features of similar type were
identified by Dresch (1968) in the Yardages of Central Asian deserts.
The formation probably represents lake deposits and consists of unfolded poorly
consolidated, bedded, yellowish silt with minor amounts of clayey, calcareous and
gypsiferous material (Geological Survey of Iran, 2006).
1.3.2.4.3.3. Makran and Baluchistan (Southeast Iran)
The late Middle Miocene saw a general regional uplift and total disappearance of the
flysch trough from this area. The elimination of the flysch trough may have been related more
to the intense tectonic deformation accompanying the vigorous onset of subduction offshore
(in the present Indian Ocean) during the late Middle Miocene rather than simple passive
filling up of the basin.
The southern platform sea was a shelf extending out from the land without the intervention of a deep
trough, and was now covered by coarse terrigenous detritus supplied by the newly uplifted landmass to
the north. Not only the Eocene flysch was being reworked, but also the Oligocene-Miocene and
Miocene flysch (Geological Survey of Iran, 2006). It is clear that the synclinal basins were tectonically
controlled. They appear as a linear chain on Landsat imagery. The immense thickness of sediments (5
000 m or more) must mean that deposition was in a tectonically controlled subsiding basin. The
intervening areas were probably the site of continuous sequences, but thinned out in the anticlinal
zone, where there was little or no subsidence. These intervening zones have now been largely
removed by erosion (Geological Survey of Iran, 2006).
1.3.2.4.3.4. Zagros
Southwest of the Zagros Main Thrust, the Neogene period is represented by the Fars
Group and Bakhtyari Formation. From the gradually rising Zagros Range, red clastic
conglomerates, sands and mudstones of the Razak Formation filled the basin from northeast
to southwest by lower Miocene time (Geological Survey of Iran, 2006). From Late Oligocene
to Early Miocene time, the Asmari Sea receded from the Zagros Basin on the Fars platform
and no important evaporite section was deposited. The evaporation products of these lagoons
and the relict sea patches are the gypsum, anhydrite and salt beds of the Gachsaran Formation.
Dendritina rangi and Miogypisna Fars Group deposition ended with the Agha Jari Formation,
a mudstone and sandstone of sequence of continental nature, 3000 m thick in the type section
(Figure1.5) (Geological Survey of Iran, 2006).
47
Figure 1.5. Stratigraphic nomenclature of rock units and age relationships in the Zagros basin (after
Rezaie and Nogole-Sadat, 2004).
48
1.4. Zagros Structure
Various schemes exist for the subdivision of the Zagros (Stocklin 1968; Falcon 1974;
Alavi and Mahdavi, 1994; Berberian 1995). It is subdivided into two main zones, divided by
major faults and/or abrupt changes in geomorphology. The original Arabia-Eurasia Zagros
suture is also known as the Main Zagros Reverse Fault. Part of this fault zone is active in a
right-lateral sense, where it is known as the Main Recent Fault (Berberian, 1995). To the
southwest, the High Zagros (HZ) Thrust Belt contains highly imbricated slices of the Arabian
margin and fragments of Cretaceous ophiolites in the southeastern Zagros, it splays off
another discontinuous series of faults for which Berberian (1995) used the term 'Zagros
Foredeep Fault, to refer to a blind 'master' thrust that causes uplift along the Zagros foreland .
This zone is up to 80 km wide and forms the topographically highest part of the Zagros, with
summits over 4 000 m above sea level. The High Zagros Thrust Belt overthrusts the second
main structural zone, the Simple Folded Zone (also known as the Simple Fold Belt, or Simply
Folded Belt) to the southwest along the High Zagros Fault spectacular 'whale-back' anticlines
of the Simple Folded Zone (deformed sedimentary cover of the Arabian plate, exposing a
Mesozoic-Cenozoic mixed carbonate-clastic succession (Figures 1.6, and 1.7). Resistant units
such as the Oligo-Miocene Asmari Limestone and the Cretaceous Bangestan Group produce
the characteristic whaleback geomorphology (Alavi and Mahdavi, 1994; Berberian 1995).
SW
NE
MZT
Suture
ZFB
Pg
SSZ
R
P
UDVZ
P
N
P
P
0
30 km
Figure 1.6. A generalized cross-section through the Zagros Mountains. Note the location of the MZRF or Main
Zagros Thrust (MZT) and the folding within the Zagros fold Belt (ZFB) Sediment ages are labeled as follows;
Neogene (N), Palaeogene (Pg), and Palaeozoic (P). Also shown are radiolarites near suture zone (R), the
Sanandaj-Sirjan Zone (SSZ), and the Urumiyeh Dokhtar volcanic zone (UDVZ) (after Stocklin, 1968).
Figure 1.7. An oblique satellite image of the Zagros Mountain range (Earthobservatory.nasa.gov.,
1992).
49
1.5. Seismicity in the Zagros Folded Belt
In general, the recent seismicity of Iran according to the International Institute of Earthquake
Engineering and Seismology (IIEES, 2004) shows the high inhomogeneity and seismic
activity scattering of the Iranian plateau. Also, the Zagros Folded Belt shows a high number
of earthquakes and no earthquakes larger than Ms = 7.0 have been experienced during the 20th
century, but shocks of magnitude over Ms = 7.0 have occurred in central and eastern Iran
(Figure 1.8).
Figure 1.8. Seismicity map of Iran. It shows the high inhomogeneity and seismic activity
dispersion of the Iranian Plateau (after International Institute of Earthquake Engineering
and Seismology-IIEES, 2004).
21
Chapter 2
The Geology of the Asmari Formation
and Associated Units
2.1. Sequence Stratigraphy of the Zagros Fold-Thrust Belt
The latest Neoproterozoic through Phanerozoic stratigraphy of the Zagros fold-thrust belt
has been revised in the light of recent investigations. The revised stratigraphy consists of four
groups of rocks, each composed of a number of unconformity-bounded megasequences
representing various tectonosedimentary settings. In the lowest group, ranging in age from
latest Precambrian to Devonian (?), the uppermost Neoproterozoic to middle Cambrian rocks
constitute a megasequence of evaporites, siliciclastic deposits, and interlayered carbonates,
which were deposited in pull-apart basins that developed by the Najd strike-slip fault system
(Alavi, 2004). This megasequence is overlain by a second one, Middle to Late Cambrian in
age, which consists of shallow, marine siliciclastic and carbonate rocks representing
deposition in an epicontinental platform (Alavi, 2004).
The overlying shales, siltstones, and partly volcanogenic sandstones of Ordovician,
Silurian, and Devonian (?) age are local remnants of stratigraphic units that were extensively
eroded during development of several major unconformities. The second group consists of
two megasequences, one Permian and the other Triassic, composed of widespread,
transgressive basal siliciclastic rocks and overlying evaporitic carbonates of an equatorial,
epi-Pangean, very shallow platformal sea (Alavi, 2004). The third group is composed of four
megasequences formed of shallow and deep-water carbonates with some siliciclastic and
evaporite deposits, which accumulated on a Neo-Tethyan continental shelf during earliest
Jurassic through late Turonian times. The fourth group comprises siliciclastic and carbonate
deposits of a largely underfilled, northwest to southeast-trending, forward and backward
migrating, late Cretaceous to Recent proforeland basin, which has evolved as an integral part
of the Zagros orogen (Alavi, 2004).
This last group consists of three megasequences (IX, X, and XI) with distinctive lateral
and vertical facies variations, which reflect specific tectonic events. Megasequence IX
comprises uppermost Turonian to middle Maastrichtian prograding and retrograding
siliciclastic and carbonate deposits, whose accumulations reflect emplacement (obduction) of
ophiolite slivers and subsequent collisional events in the Zagros orogen (Alavi, 2004).
Megasequence X consists of uppermost Maastrichtian to upper Eocene siliciclastic and
carbonate rocks, which deposited first progradationally in front of the Zagros orogenic wedge
with reduced contractional tectonic activity, and then retrogradationally due to intensified
thrust stacking in the interior parts of the orogen. Megasequence XI consists of Oligocene
and lower Miocene carbonate strata deposited retrogradationally shortly after a period of
intensified late Eocene thrust faulting in the deformational wedge, and an overlying
succession of upward-coarsening, northeasterly-derived siliciclastic deposits of lower
Miocene to Recent age which are composed of erosional by products of the southwestvergent Zagros thrust sheets (Alavi, 2004).
2.1.1. Tectonic Setting
The Zagros orogen (Figure 2.1) is interpreted as the product of three major sequential
geotectonic events: (1) subduction of the Neo-Tethyan oceanic plate beneath the Iranian
lithospheric plates during Early to Late Cretaceous time, (2) emplacement (obduction) of a
number of Neo-Tethyan oceanic slivers (ophiolites) over the Afro-Arabian passive
continental margin in Late Cretaceous (Turonian to Campanian) time, and (3) collision of
the Afro-Arabian continental lithosphere with the Iranian plates in Late Cretaceous and later
times (Alavi and Mahdavi, 1994). The orogen is bounded to the northwest by the East
Anatolian left-lateral strike-slip fault (EAF) and to the southeast by the Oman Line (OL)
24
(Falcon, 1969), which is here considered to be a transform fault inherited from the opening
of Neo-Tethys. The orogen consists of three parallel belts:
(1) the Urumieh-Dokhtar magmatic assemblage (UDMA), which forms a subduction-related,
distinctively linear and voluminous magmatic arc composed of tholeiitic calc-alkaline, and
K-rich alkaline intrusive and extrusive rocks (with associated pyroclastic and volcaniclastic
successions) along the active margin of the Iranian plates; (2) the Zagros imbricate zone
(ZIZ) (the “Sanandaj-Sirjan Zone”, as redefined by Alavi and Mahdavi (1994), after
Stocklin, 1968a, 1977), which is a zone of thrust faults that have transported numerous slices
of metamorphosed and non-metamorphosed Phanerozoic stratigraphic units of the AfroArabian passive continental margin, as well as its obducted ophiolites, from the collisional
suture zone on the northeast toward interior parts of the Arabian Craton to the southwest;
and (3) the Zagros fold-thrust belt (ZFTB),which forms the less strained external part of the
orogen, and consists of a pile of folded and faulted rocks composed of 4 to 7 km of mainly
Palaeozoic and Mesozoic successions overlain by 3 to 5 km of Cenozoic siliciclastic and
carbonate rocks resting on highly metamorphosed Proterozoic Pan-African basement that
was affected by the late Neoproterozoic–Cambrian Najd strike-slip faults (for example,
Brown and Jackson, 1960; Moore, 1979; Agar, 1987; Husseini, 1988).
Elevation more than 2000 m
Elevation less than 2000 m
Oil field
Gas field
Figure 2.1. The Zagros orogenic belt and its subdivisions. Abbreviations; EAF – East Anatolian
fault; OL- Oman line; UDMA – Urumieh-Dokhtar magmatic arc; ZDF – Zagros deformational
front; ZFTB – Zagros fold-thrust belt; ZIZ – Zagros imbricate zone: ZS – Zagros suture; Red dots
show location of the stratigraphic columns. Hydrocarbon fields of the region (oil in green and gas in
pink) are also shown (after Alavi, 2004).
The southwestern boundary of the Zagros fold-thrust belt defines the present-day Zagros
deformational front (ZDF), to the southwest of which deformation has not yet propagated
(Alavi, 2004).
22
2.1.2. Stratigraphy
More than a hundred stratigraphic columns have been studied by Alavi and Mahdavi
(1994) from both subcrop (well) and outcrop section in various parts of the Zagros belt.
Based on this database and available published and unpublished stratigraphic,
sedimentological, and petrographic information, as well as field and laboratory observations a
description for each stratigraphic unit has been prepared (Alavi and Mahdavi, 1994).
The latest Neoproterozoic-Phanerozoic stratigraphy of the Zagros fold-thrust belt is
represented by four major groups of rocks that are defined based on their tectonosedimentary
features. Each group consists of a number of unconformity-bounded megasequences, each of
which represents a discrete sedimentary cycle and consists of a number of lithostratigraphic
units (Figures 2.2 and 2.3).
2.1.2.1. Lithostratigraphic Units of the Zagros Fold-Thrust Belt
2.1.2.1.1. Neoproterozoic to Devonian (?) Pull-apart Basin and Epicontinental Platform
Deposits
Hormus (uppermost Proterozoic to Middle Cambrian): evaporites (mainly halite and
anhydrite with subordinate gypsum near top), with interlayered volcanics in upperpart.
Barut (Lower Cambrian): gray stromatolitlitic dolomite (Alavi, 2004).
Zaigun (Lower Cambrian): red, purple, grey green nonmarin shale.
Lalun (upper Lower Cambrian): red and purple sandstones, siltstone, and shale with
polymict pebble conglomerate near top.
Mila (Middle to lower Upper Cambrian): white orthoquartzite and quartzose sandstone,
partly stromatolitic limestone and dolomitic (Alavi, 2004).
Ilbeyk (Upper Cambrian): grey to greenish grey, trilobite-bearing, micaceous marine shale.
Ordovician strata (including Lower to Middle Ordovician Zard Kuh): greenish gray
trilobite-bearing and/or brachiopod-bearing, partly graptolitic shale.
Silurian strata (including Gahkum shales): unconformity-succession of dark gray to black,
Orthoceras-bearing and graptolite-bearing, shale and thin sandstone. (Alavi, 2004).
Devonian strata: unconformity-bounded succession of light gray, partly conglomeratic
sandstone interbedded with siltstone and shale (Alavi, 2004).
2.1.2.1.2. Permian to Triassic Epi-Pangean Platform Deposits
Faraghan (Lower Permian): light gray polymict conglomerate overlain by cross-bedded
quartzarenites, siltstone and red shale.
Dalan (Lower to Upper Permian); medium to thick-bedded oolitic to micritic dolomite,
dolomitic limestone with intercalations of evaporites.
Kangan (Lower Triassic): gray Claraia-bearing and partly oolitic limestone and dolomitic
limestone with intercalations of shale.
Khaneh Kat (Lower to lower Upper Triassic): thin bedded dark gray dolomite and dolomitic
limestone.
Aghar (medial Triassic): thin interval (~50 m thick) of brown shale and silty argillite with
thin intercalations of dolomite, anhydrite, and siltstone (Alavi, 2004).
Dashtak (Middle to Upper Triassic): massive to thick-bedded, dolomite, dolomitic
limestone interbedded with evaporites (Alavi, 2004).
23
Time Units
L.Miocene
Formation
Lithology
Gachsaran
Alternating of
anhydrite, gypsum
salt, colored marls
marlylimestone
sandstone
Oligo Miocene
Asmari
Limestone,
marlylimestone
dolomitic limestone,
marlstone, with
thin interbeded
of shale
L.Oligocene
Paleocene
Pabdeh
Alternating of
marlstone,
marlylimestone,
and shale
Figure 2.2. Stratigraphy column of the Zagros fold-thrust belt of Iran (after Alavi, 2003).
21
Description
2.1.2.1.3. Jurassic to Upper Cretaceous Continental-Shelf Deposits
Neyriz (Lower Jurassic): thin-bedded dolomite and greenish gray shale grading upward to
quartzose sandstone.
Surmeh (Lower to Upper Jurassic): massive gray Lithiotis-bearing dolomite and limestone
(Alavi, 2004).
Sargelu (MiddleJurassic; Bajocian to Bathonian): thin interval of dark gray, organic-rich
papery shale.
Najmeh (Middle to Upper Jurassic; Callovian to Oxfordian): cyclic alternations limestones
(Alavi, 2004).
Alan/ Adaiyah (Upper Jurassic): evaporites (gypsum, anhydrite), interlayered with thin
intervals of limestone and shale.
Hith/ Gotnia (Upper Jurassic): evaporites (anhydrite, halite).
Fahliyan (uppermost Jurassic-Cretaceous; Tithonian to Hauterivian): massive gray to brown
oolitic and pelletal limestone.
Dariyan (Lower Cretaceous; upper Aptian): thick-bedded gray to brown, Orbitulina
limestone.
Kazhdumi (Lower Cretaceous; Albian): dark, ammonoid-bearing limestone, interbedded
with dark argillaceous limestone and shale (Alavi, 2004).
Garau (Lower to Upper Cretaceous; Neocomian to upper Toronian): dark gray to black
radiolarian and ammonoids-bearing shale, limestone and marl.
Sarvak (Lower to Upper Cretaceous; upper Albian to upper Turounian): gray limestone.
2.1.2.1.4. Upper Cretaceous to Recent Proforeland Basin Deposits
Surgah (Upper Cretaceous; uppermost Turonian to Santonian): dark gray to brown,
calcareous shale and limestone.
Ilam (Upper Cretaceous; Santonian to Campanian): light gray shallow-marine limestones
with intercalations of black shale (Alavi, 2004).
Gurpi (Upper Cretaceous; Santonian to Maastrichtian): dark bluish gray Globigerinabearing marl and marly limestone.
Amiran (Upper Cretaceous; Maastrichtian and probably older): dark gray to reddish brown
conglomerate, sandstone, siltstone, shale (Alavi, 2004).
Tarbur (Upper Cretaceous; Maastrichtian): light gray, thick-bedded to massive, rudist
limestone with a basal conglomerate.
Sachun (uppermost Maastrichtian to Palaeocene): green argillite, red shale, evaporites.
Kashkan (Palaeocene to Middle Eocene): dark reddish brown polymict conglomerate
sandstone, siltstone, and red shale. (Alavi, 2004).
Shahbazan (Eocene): Brown Nummulites-bearing dolomitic limestone. (Alavi, 2004).
Pabdeh (upper Paleocene to lowermost Oligocene): thin-bedded gray and greenish blue
calcareous shale and marl.
Jahrum (Paleocene to upper Eocene): gray dolomite interbedded with Alveolina-bearing and
Nummolites-bearing dolomitic limestone (Alavi, 2004).
Ahwaz (medial to Upper Oligocene): well bedded, light gray, calcarenite interlayered with
sandy limestone, sandstone and sandy to silty shale.
Kalhur (Oligocene, locally lower Miocene): evaporites interbedded with gray shale.
Asmari (Oligocene to lower Miocene): medium-bedded to thick-bedded, locally shelly or
oolitic, Nummulites-bearing limestones (grainstone, packstone, wackestone) shoaling
upward above a thin basal conglomerate from fine-grained (low-energy) deep-marine marly
limestone to high-energy shallow-marine skeletal grainstone; composed of a number of
25
26
Figure 2.3., A, B, C, D. Four stratigraphic correlation profiles across the Zagros fold-thrust belt of Iran. See Figure 2.1 for locations of the stratigraphic profiles. Three
megasequences (IX, X, and XI of Figure2.2) of the proforeland basin are distinguished. The stratigraphic columns restored to their pre-Zagros-deformation positions.
The latest Turonian regional unconformity is chosen as the datum. Non-Iranian stratigraphic nomenclatures are shown in black (after Alavi, 2004).
27
Figure 2.3. continued
28
Figure 2.3. continued
29
Figure 2.3. continued
sequences; an unconformity-bounded, highly prolific reservoir; interpreted as transgressiveregressive foredeep facies of the proforeland basin.
Razak (Oligocene to lower Miocene): variegated (gray, red, green), including polymict
conglomerate, argillaceous limestone; interfingers with Asmari limestones toward the
southwest, and also interfingers with and Asmari limestones toward the southwest, and
interfingers with lower Gachsaran evaporitic beds to the northeast; deposited in the distal
wedge-top depozone of the proforeland basin.
Gachsaran (lower Miocene): variable thickness and lithology including alternations of gray
evaporites (gypsum, anhydrite, subordinate halite), dark red shale, gray to red marl, sandstone
and locally conglomeratic.
Mishan (lower to middle Miocene): gray marl, calcareous shale and sandstone (Alavi, 2004).
Agha Jari (upper Miocene to Pliocene): composed of carbonate-clast and polymict
conglomerate, calcarenite, gray sandstone, siltstone and marl.
Lahbari (upper Miocene to Pliocene): calcareous argillite, siltstone and sandstone.
Bakhtiari (Pliocene to Pleistocene): massive to thick-bedded polymict conglomerate,
sandstone, siltstone, and shale. (Alavi, 2004).
2.2. Stratigraphic Units of the Asmari Formation
2.2.1. Lithostratigraphic Units
The name Asmari Formation is derived from Mount Asmari in southwest of Masjed
Soleyman, northwest Haftgel in the Zagros Fold belt (Thomas, 1948). The Oligo-Miocene
Asmari Formation of the Zagros Mountains of southwest Iran is one of the world’s most
important reservoirs. Despite this, its sedimentology has received relatively little attention,
particularly in terms of outcrop studies. This is surprising, as it can be examined in exposures
within ravines cutting through the huge and striking whaleback anticlines that make up the
Zagros fold belt. Many of these exposures occur close to existing fields, allowing the
opportunity to see the reservoir at surface.
The Asmari Formation lithologically comprises medium-bedded to thick-bedded, locally
shelly or oolitic, Nummulites-bearing limestones (grainstone, packstone, wackestone)
shoaling upward above a thin basal conglomerate from fine-grained (low-energy) deepmarine marly limestone to high-energy shallow-marine skeletal grainstone; composed of a
number of sequences; an unconformity-bounded, highly prolific reservoir; interpreted as
transgressive-regressive foredeep facies of the proforeland basin.
Lithostratigraphic units of Asmari Formation were introduced by Adams and Bourgeois
(1965). These units coincide with biostratigraphic units of Asmari Formation. The Asmari
limestone is typically around 500 m in thickness, and is generally divided into three parts:
 The Lower Asmari is marly in character near the base and overlain by foraminiferal
and coralline algal limestones
 The Middle Asmari comprises dolomitised, lagoonal limestones
 The Upper Asmari is more evaporitic.
The detailed sedimentological data collected during the fieldwork has been used to
develop a sequence stratigraphic framework, subdividing the Asmari limestone into four
cycles, and then into 33 subordinate cycles. This framework has then been applied regionally
to explain the distribution of lithofacies within the Asmari Formation across the Zagros. The
deposition of the contemporaneous Ghar and Ahwaz sandstone members is examined,
suggesting that the northeastward progradation of these sand bodies may have been
31
controlled by relative changes in sea level. This may in turn allow the potential stratigraphic
position of low-stand wedges to be predicted. The Ahwaz Asmari formation (Figure 2.4 and
2. 5) has 16 wells that have recovered cores. The mixed siliciclastic/ carbonate reservoir has
undergone post depositional diagenesis, which have had an impact on reservoir
characteristics. Calcite cementation and dissolution, dolomitization and particularly
precipitation of anhydrite cements have destroyed porosity in both the carbonates and
siliciclastic sands in the Ahwaz field. In this oil field, the Lower Asmari sands were deposited
in a restricted area during sea-level Low-stands, while the Middle and Upper Asmari were
deposited over a widespread carbonate ramp and contain Transgressive and High stand sands.
The development of the thick Kalhur evaporites to the northwest has been addressed in
Figures 2.4 and 2.6.
A relatively 15º angular unconformity of late Eocene-early Oligocene age occurs between
the Pabdeh and Asmari formations about 75 km west of Shiraz along the northeastern part of
the Zagros Simply Folded Zone (Tectonic movement locally folded and uplifted the Pabdeh
Formation exposing it to erosion along the crests of anticlines before this unconformity was
buried beneath the Asmari Limestone). However, to the NE of this unconformity, the shelf
deposits of the Jahrom Formation (time-equivalent of the Pabdeh Formation) do not show
this relationship (Motiei, 1993).
Instead, they have been exposed to subaerial weathering (James & Wynd 1965; Mina et al.,
1967; Motiei 1993) ever since the onset of this tectonic movement. The unconformity
between the Pabdeh and Asmari Formation and its weathering that this phase of orogeny
began with a few individual folds and uplifted the area to the northeast at the end of the
Eocene.
In many places within the Simply Folded Zone of the Zagros (e.g. 120 km west and 5
km east of Shiraz), the Razak Formation onlaps the Asmari Formation. One of the most
obvious exposures of this onlap crops out some 100 km south of Shiraz. In this locality,
the top 20 m of the Asmari Limestone exhibits palaeo-weathering along joints suggesting
subaerial exposure of the Asmari near the crest of an anticline. A monomict conglomerate
with clasts composed only of the Asmari Limestone occurs at the top of the Asmari
Limestone 5 km east of Shiraz (Fars Province). Similar conglomerates are reported at the
same stratigraphic level in the northwest Zagros of Iraq (Motiei, 1993). Such onlaps and
conglomerates are due to gentle movements at the end of Asmari times (Burdigalian).
They indicate that particular anticlines capped by the Asmari Formation reached wavebase or even subaerial conditions in these areas. Hence, present outcrops of the Asmari
Formation in these areas of the Simply Folded Zone record local erosion of highs uplifted
by folding so that younger sediments were deposited only along syncline axes (Hessami et
al., 2001).
In this part, the stratigraphic relationships between various units of Asmari Formation and
also single stratigraphic columns (Figures 2.5 to 2. 8) for each member at different localities
in Zagros region have been introduced (see Figure 2.4. for location).
Recently, some research has been done on the stratigraphy of the Asmari Formation in the
Zagros region. For example Nadjafi et al. (2006) studied depositional history and sequence
stratigraphy of outcropping tertiary carbonates in the Jahrum and Asmari Formations in
Shiraz area (Fars Province). They show that the Asmari Formation rests on the thin bedded
limestones/dolomites of the Jahrum Formation (Palaeocene-Eocene) and reported on the
lithofacies characteristics of these two formations using data from three measured outcrop
sections in study area.
34
Ab Teymoor Oil field
Ahwaz Oil field
Changoleh-well, No-1
Lali section
Kuh Asmari section
40
IRAN
30
0
200 km
50
60
Figure 2.4. Correlation chart of the tertiary of southwest Iran (after Vaziri et al., 2006, adopted from Ala,
1982). The line indicates the correlation direction and the triangles show locality of some geological columns
that are described in Figures 2.5 to 2.8.
From field and petrographic data, they have identified four major lithofacies and twelve
subfacies which are interpreted to have been deposited in open-marine, shoal, lagoon and
tidal flat settings. Also, they showed that the Asmari and Jahrum Formations constitute two
separate depositional sequences which are separated by a thin palaeosol, representing a typeone sequence boundary which can be correlated with global curves of relative sea-level. Each
depositional sequence is composed of several metre-scale shallowing-upward parasequences.
This is the first time that the Asmari and Jahrum Formations have been differentiated in the
study area. This study will lead to a better understanding of the Asmari Formation in the
subsurface in other parts of the Zagros Basin.
Vazirimoghadam et al. (2005) studied microfacies, palaeoenvironments and sedimentary
sequences of Asmari Formation in Lali, Kuh-Asmari and Khaviz area at Khuzestan Province
(Figures 2.7 and 2. 8). Detailed petrographic analysis of the deposits led to the recognition of
ten microfacies types. In addition, five major depositional environments were identified in the
Asmari Formation.
32
These include tidal flat, shelf lagoon, shoal, slope and basin environmental settings and
are interpreted as a carbonate platform developed in an open shelf situation but without
effective barriers separating the platform from the open ocean. The Asmari carbonate
succession consists of four, thick shallowing- upward sequences (third-order cycles). No
major hiatuses were recognized between these cycles. Therefore, the contacts are interpreted
as SB2 sequence boundary types. The Pabdeh Formation, the deeper marine facies equivalent
of the Asmari Limestone is interpreted to be deposited in an outer slope- basin environment.
The microfacies of the Pabdeh Formation show similarities to the Asmari Formation.
Unit
Thickness
Description
Stage
Epoch
Unit
Thickness
Formation
Stage
Epoch
Ga
Lithology
Formation
AHWAZ SS. MEMBER- OIL WELL, NO.6
AHWAZ OIL FIELD
SUPPLIMEMTARY SECTION OF AHWAZ SS.MEMBER
Oil well no. 1, Ab Teymoor oil field
Ga
Evaporites
Lithology
Description
Evaporites
Limestone
Limestone
Sandstone
213
?
Oligocene
Aquitanian
Dolomite
AHWAZ Sandstone Mbr.
Sandstone
A S M A R I
366
A H W A Z S a n d s t o n e Mbr.
Miocene
Lower Miocene
Sandstone
U
A S M A R I
Burdigalian
147
Limestone
Sandy limestone
M
Pb
Shale
Oligocene
Marly Limestone
L
Pb
Figure 2.5. Stratigraphic column of Ahwaz Sandstone member in oil well No. 1, Ab Teymoor Oil field
(supplementary section (left- 1968) and oil well No.6, In Ahwaz Oil field (right- 1965), (after Motiei,
1993).
33
Sequence stratigraphy of Asmari Formation was also studied by Hassan Mohseni et. al
(2006) on three outcrops and two oil well sections. According to petrography and field
observations, the formation is divided into three parts and comprises six microfacies
assemblages as: A (open marine); B (bar/shoal); C (lagoon); E (tidal flat) and F (supratidal).
Unit
Thickness
Description
U
Evaporites
135
Description
Lithology
Evaporites
4
55
As
Lithology
Ga
Burdigalian
Unit
Thickness
Formation
Stage
Epoch
KALHUR EVAPORITE MEMBER /SUPLIMENTARY SECTION
Changoleh-well No. 1
Formation
Stage
Epoch
LITHOSTRATIGRAPHY OF ASMARI FORMATION / Khaviz Section
3
Limestone
Alternation of thick to medium
bedded
Limestone, marly limestone
with gastropoda shells
A S M A R I
Salt
Aquitanian
Oligo-Miocene
KALHUR Evaporite Mbr.
280
A S M A R I
Aquitanian
Lower Miocene
M
Alternation of thick to
medium bedded limestone
with some marls intercaations
gastropoda shells
146
Massive limestone
cream to gray in color
with remains of gastropoda
and lepidocyclina shells
karstified
2
Chatian
Anhydrite
L
46
EO/OLIGO
Shale, Marl
1
Thick to medium bedded
limestone with intercalations
of shale and marls
with remains of shells and
big lepidocyclina
Pb
Figure 2.6. Stratigraphic column of Kalhur
evaporite member/ Supplementary section,
Changoleh, well No.1 (after Motiei, 1993).
Pb
Figure 2.7. Lithostratigraphic columns of the Asmari
Formation in the Khaviz section, Khuzestan Province
(after Vazirimoghdam et al., 2005).
On a sequence stratigraphic framework, the lower Asmari was deposited in HST
(highstand system tract) stage, whereas TST started during the deposition of underlying
Pabdeh Formation and transgression reach to highest level (mfs- maximum flooding surface)
just at the boundary of the Asmari and Pabdeh Formations. Succeedingly HST stage is
marked by algal boundstones and late HST by lagoon facies (dolomudstone, miliolidae
wackestone). Dolomitization increased intercrystaline porosity of the Asmari carbonate
reservoir. In the Renu surface section, only the lower Asmari was deposited whereas in the
Siahgel surface section, only the middle Asmari was deposited on shale beds of Pabdeh
Formation. The middle Asmari is marked as early HST (algal boundstone) and late HST
sediments composed of lagoonal facies (miliolidae wackestones and evaporites). This
sequence terminated with sandstone facies with hematite cements that imply a Type 1
sequence boundary. In brief the middle Asmari comprises two stages of HST, one LST
(lowstand system tract), and one TST.
31
The Upper Asmari exposed only in the Dezful Embayment, comprises two HST, two TST;
the later began with echinoderm wackstone microfacies. Early HST sediments are
dolomitized lime mudstones but late HST are miliolidae wackestone, algal wackstone,
ostracod wackestone and pellet grainstone that suggest a lagoon setting. Dolomitization
occurred in the early HST stage and developed porosity of the formation. Sequence boundary
is Type 2 and no evidence of exposure was observed.
Unit
Formation
Stage
Thickness
4
3
Burdigalian
88
Alternation of thick, medium
and thin bedded limestone
with gastropoda and bivalvia shells
A S M A R I
3
Oligo-Miocene
U
196
U
102
41
Description
Thick to medium bedded
limestone with marly limestone
intercalations
77
2
31
1
2
U
M
58
Late Aquitanian
M
Thick to massive cherty limestone
with bivalvia and echinoderma shells
Chatian
Lithology
Evaporites
Limestone, thick to massive
with big bivalvia shells
and stromatolitic limestone
Alternations of marly limestone
with medium bedded limestone
A S M A R I
Burdigalian
Aquitanian
Ga
Evaporites
4
Oligo-Miocene
Description
64
Ga
Lithology
LITHOSTRATIGRAPHY OF ASMARI FORMATION / Kuh Asmari
TANGE Gel torsh
Epoch
Unit
Thickness
Formation
Stage
Epoch
LITHOSTRATIGRAPHY OF ASMARI FORMATION / Lali Section
1
Alternation of thick-massive
and medium bedded limestone
Thick to massive limestone
and intercalations of
marly limestone, nodular
with gastropoda shells
Thin to medium bedded
marly limestone with marls and
shale intercalations
L
Alternation of thick to medium
bedded limestonand green marls
karstified,
with bivalvia and lepidocylina shells
Pb
Pb
Figure 2.8. Lithostratigraphic columns of the Asmari Formation in Lali and Kuhe Asmari sections –
Khuzestan Province (after Vazirimoghadam et al., 2005).
2.2.2. Biostratigraphic Units of the Asmari Formation
The biostratigraphic units of the Asmari Formation was first described by Wynd (1965)
and revised by Adam and Bourgeois (1967). They divided the Asmari Formation into three
units based on the presence of foraminifera's assemblage zones (Table 2.1).
Table 2.1. Asmari Formation assemblage zones (after Adams and Bourgeois, 1965).
Biozone
Borelis melo-Meanropsina iranica
Elphidium sp. 14-Miogipsina
Archaias asmaricus- Archaias hensoni
Eulepidina- Nphrolepidina- Nummulites
Lithostratigraphic unit
Upper Asmari
Middle-Upper Asmari
Lower-Middle Asmari
Lower Asmari
35
Age
Burdigalian
Late Aquitanian
Early Aquitanian
Oligocene
Chapter 3
Rock Mass Description
3.1. Introduction
Rock mass classifications constitute the foundation of experimental geotechnical design
and are widely used in rock engineering. It is proven that the classification of rock masses
can be used as a powerful tool in rock engineering if the parameter estimations are done
accurately. In fact, in most projects, it forms the basis of complicated underground designs,
for example an underground Ice-hockey stadium in Gjovik of Norway with 60 m diameter
was designed based on rock mass classification. The minimum and maximum ratings in these
classifications are designated to the weakest and strongest rock mass respectively and each
classification parameter significantly governs the final rating of rock mass quality (Singh and
Goel, 1999). However, classification is frequently used in the initial phase of a project to
foresee the rock mass quality and the probable support required. The consequence is an
assessment of the stability quantified in subjective terms such as bad, fair, good and excellent
conditions.
Several rock mass quantitative classification systems are established in South Africa, United
States, Europe and India which present satisfactory outcomes mainly due to:
 Better relationship between geologists, designers, contractors and engineers;
 Coincidence with observations, experiences and engineering judgments and
 Introducing quantitative results for engineers.
The classification systems were updated with new developments in the rock support
technology over the past 50 years. These improvements started with steel arches and
progressed over time to more innovative methods such as rockbolts and reinforced shotcrete
(with steel fibre) as well as instrumentation and monitoring devices for geotechnical control
purpose (Singh and Goel, 1999).
The early 1960s were very important in the general development of rock engineering
throughout the world, due to several disastrous failures that happened which obviously
established that, in rock and soil, ‘we were over-stepping the limits of our ability to predict
the consequences of our actions’ (Terzaghi and Voight, 1979).
The failure of the Malpasset concrete dam in France in 1959 and the Vajont dam in Italy had
a major influence on rock mechanics in geotechnical engineering and a large number of
articles were introduced on the possible reasons of the failures (Jaeger, 1972). These
incidents were responsible for the commencement of several research programmes that
resulted in major progress in the techniques used in rock engineering.
The four most commonly used rock mass classification systems today are the
geomechanics classification or rock mass rating (RMR, Bieniawski, 1974- South Africa) the
Norwegian Geotechnical Institute (NGI) index (Q system, Barton et al., 1974), rock quality
designation (RQD), which was introduced by Deer in 1963 as an index for assessing rock
quality quantitatively, and also recently a classification introduced by Hoek et al. (1995)
named geological strength index (GSI). In this research, the Asmari Formation succession
rock mass has been classified by these four methods. Since different
classification/characterisation systems pay attention to different parameters, it is often
recommended that at least two methods should be used when classifying a rock mass (Hoek,
2000).
36
3.2. Engineering Rock Mass Classification
3.2.1. Rock Quality Designation (RQD)
Deere (1963) introduced an index to assess rock quality quantitatively, called the rock
quality designation (RQD). The RQD (Table 3.1) is a core recovery percentage that is
indirectly based on the number of fractures and the amount of softening in the rock mass that
is observed from drill cores. Only the intact pieces with a length longer than 100 mm are
summed and divided by the total length of the core run (Deere, 1968).
It is used as a standard parameter in drill core logging and its greatest value is perhaps its
simplicity and quick determination, and also that it is inexpensive. RQD is to be seen as an
index of rock quality where problematic rock that is highly weathered, soft, fractured, sheared
and jointed is encountered in rock mass. This means that the RQD is simply a measurement
of the percentage of good rock recovered from an interval of a borehole (Hoek, 2000).
The International Society of Rock Mechanics (ISRM) Commission on Standardization of
Laboratory and Field Tests recommends RQD calculations using variable run lengths to
separate individual beds, structural domains and weakness zones so as to indicate any
inherent variability and provide a more accurate picture of the location and width of zones
with low RQD values (Hoek, 2000). The relationship between the numerical value of RQD
and the engineering quality of the rock mass as proposed by Deere (1968) is given in Table
3.1. RQD can also be found from the number of joints/ discontinuities per unit volume (Jv)
on the rock surface. Palmstrom (1982) presented a relationship for a clay free rock mass
along a tunnel:
RQD = 115- 3.3 Jv
(3.1)
where Jv is known as the volumetric joint count and is the sum of the number of joints per
unit length for all joint sets in a clay free rock mass. For Jv < 4.5, RQD = 100.
Palmstrom (1996) suggested a method to achieve better information from the surface instead
of drill cores, though RQD depends on the borehole orientation. In principle, it is based on
the measurement of the angle between each joint and the surface or the drill hole. The
weighted joint density (wJd) is for measurements on rock surfaces and given by:
(3.2)
And for measurements along a drill core or scan line:
(3.3)
where δ1 is the intersection angle, i.e., the angle between the observed plane or drill hole and
the individual joint, A is the size of the observed area in m2 and L is the length of the
measured section along the core or scan line.
Table 3.1. Correlation between RQD and rock mass quality (after Deere, 1968).
RQD (%)
< 25
25- 50
50- 75
75- 90
90- 100
Rock Quality
Very Poor
Poor
Fair
Good
Excellent
The major rock mass classifications and parameters included in some of the classification
systems are presented in Table 3.2.
37
3.2.1.1. Disadvantages of RQD
According to Merritt (1972), the RQD system has limitations in areas where the joints
contain clay fillings. The clay fillings would reduce the joint friction and the RQD would be
high despite the fact that the rock is unstable. It is unlikely as mentioned by Douglas et al.
(1999) that all defects found in the boreholes would be of significance to the rock mass
stability.
The RQD is not a good parameter in the case of a rock mass with joint distances near 100
mm. If the distance between continuous joints is 105 mm (core length), the RQD value will
be 100%. If the distance between continuous joints is 95 mm, the RQD value will be 0%. If
the parameter Jv (Palmstrom, 1982) should be used, its value would be close to 10 joints/
metre for both of the cases described above (Helgstedt, 1997). As mentioned by Milne et al.
(1991), a rock mass with a calculated RQD of 100% could have 3 joint sets with an average
spacing of 0.4 m or 1 joint set with spacing of several metres.
The RQD value may change significantly depending on the borehole orientation relative to
the geological structure and according to Hoek et al. (1993), the use of the volumetric joint
count is useful in reducing this dependence.
3.2.2. Rock Mass Rating (RMR)
Bieniawski (1973) introduced the Geomechanics Classification also named the Rock Mass
Rating (RMR), at the South African Council of Scientific and Industrial Research (CSIR).
The rating system was based on Bieniawski’s (1984) experiences in shallow tunnels in
sedimentary rocks. Over the years, this system has been successively refined as more case
records have been examined and Bieniawski has made significant changes in the ratings
assigned to different parameters. The following six parameters are used to classify a rock
mass using the RMR system (Table 3.3):
1. Uniaxial compressive strength of rock material;
2. Rock Quality Designation (RQD);
3. Spacing of discontinuities;
4. Condition of discontinuities;
5. Groundwater conditions; and
6. Orientation of discontinuities.
In applying this classification system, the rock mass is divided into a number of structural
regions and each region is classified separately. The boundaries of the structural regions
usually coincide with a major structural feature such as a fault or with a change in rock type.
In some cases, significant changes in discontinuity spacing or characteristics, within the same
rock type, may necessitate the division of the rock mass into a number of small structural
regions. The Rock Mass Rating system is presented in Table 3.3 giving the ratings for each of
the six parameters listed above. These ratings are summed to give the RMR value.
Bieniawski (1989) published a set of guidelines for the selection of support in tunnels in rock
for which the value of RMR has been determined (Table 3.4). Note that these guidelines have
been published for a 10 m span horseshoe shaped tunnel, constructed using drill and blast-
38
Table 3.2. Major rock mass classification/characterisation systems (modified after Palmstrom 1995).
Name of
Classification
Rock load
Theory
Author and First
version
Terzhagi, 1946
USA
Stand up time
Lauffer, 1958
Austria
NATM
Rebcewicz
1964/65 and 1975
Austria
RQD
Deere et al, 1966
USA
A recommended
rock
classification for
rock mechanical
purpose
The unified
classification of
soils and rocks
i)RSR concept
Country of origin
Applications
Form and Type
Remarks
Tunnels with steel
supports
Unsuitable for
modern
tunneling
Tunnelling in
incompetent
(overstressed)
ground
Descriptive F
Behaviour F
Functional
Descriptive F,
General T
Descriptive F
Behaviouristic F,
Tunnelling
concept
Core logging,
tunnelling
Numerical F,
General T
For input in rock
mechanics
Descriptive F,
General T
Tunnelling
Patching and
Coates, 1968
Deere et al, 1969
USA
Based on particles
and blocks for
communication
Descriptive F,
General
Wickham et al,
1972
USA
Tunnel with steel
support
Numerical F,
Functional T
Tunnels, mines,
foundations etc.
Numerical F,
Functional T
Tunnels, large
chambers
RMR-system
(CSIR)
Bieniawski 1974
South Africa
Q- system
Barton et al, 1974
Norway
Mining RMR
Laubscher, 1975
Mining
The typological
classification
ii) The Unified
Rock
Classification
System (URCS)
Basic
geotechnical
description
(BGD)
Rock mass
strength (RMS)
Modified basic
RMR (MBR)
Matula and
Holzer, 1978
For use in
communication
Numerical F,
Functional T
Numerical F,
Functional T
Descriptive F,
General
USA
For use in
communication
Descriptive F,
General
---
For general use
Descriptive F,
General
Simplified rock
mass rating
Slope mass
rating
Ramamurthy
Arora
Geological
Strength IndexGSI
Rock mass
Number- N
Rock mass
index- RMi
Williamson, 1980
ISRM, 1981
Stille et al, 1982
Conservative
Utilized in
squeezing
ground
conditions
Sensitive to
orientation
effects
Not useful with
steel fibre
shotcrete
Unpublished
based case
records
Numerical F,
Functional T
Numerical F,
Functional T
Modified RMR
Mines and tunnels
Numerical F,
Functional T
Modified RMR
and MRMR
Sweden
Cummings et al,
1982
Brook and
Dharmaratne,
1985
Romana, 1985
Spain
Slopes
Numerical F,
Functional T
Ramamurthy and
Arora, 1993
India
For intact and
jointed rocks
Numerical F,
Functional T
Hoek et al, 1995
---
Mines and tunnels
Numerical F,
Functional T
Geol et al, 1995
India
Arild Palmstrom,
1995
Norway
mining
Numerical F,
Functional T
Rock engineering,
communication,
characterisation
Modified Deere
and Miller
approach
Stress- free Qsystem
Numerical F,
Functional T
methods, in a rock mass subjected to a vertical stress < 25 MPa (equivalent to a depth below
surface of < 900 m). The relationship between stand-up time, span and RMR classification in
tunnels introduced by Bieniawski is shown in Figure 3.1.
39
Table 3.3. Rock Mass Rating (RMR) System (after Bieniawski 1989).
11
Cases history: Tunneling
Mining
Figure 3.1. Relationship between Stand-up time, span and RMR classification (after Bieniawski
(1989).
Table 3.4. Guidelines for excavation and support of 10 m span rock tunnels in accordance with
the RMR system (after Bieniawski 1989).
2.1.3. Rock Tunneling Quality Index, Q
On the basis of an evaluation of a large number of case histories of underground
excavations, Barton et al (1974) of the Norwegian Geotechnical Institute proposed a
14
Tunneling Quality Index (Q) for the determination of rock mass characteristics and tunnel
support requirements. The numerical value of the index Q varies on a logarithmic scale from
0.001 to a maximum of 1 000 and is defined by:
(3.4)
Where;
RQD is the Rock Quality Designation
Jn is the joint set number
Jr is the joint roughness number
Ja is the joint alteration number
Jw is the joint water reduction factor
SRF is the stress reduction factor
In explaining the meaning of the parameters used to determine the Q value, Barton et al
(1974) offer the following comments:
The first quotient (RQD/Jn), representing the structure of the rock mass, is a crude measure
of the block or particle size, with the two extreme values (100/0.5 and 10/20) differing by a
factor of 400.
The second quotient (Jr/Ja) represents the roughness and frictional characteristics of the joint
walls or filling materials. This quotient is weighted in favor of rough, unaltered joints in
direct contact.
The third quotient (Jw/SRF) consists of two stress parameters. SRF is a measure of:
1. Loosening load in the case of an excavation through shear zones and clay bearing rock,
2. Rock stress in competent rock, and
3. Squeezing loads in plastic incompetent rocks.
It can be regarded as a total stress parameter. The parameter Jw is a measure of water
pressure, which has an adverse effect on the shear strength of joints due to a reduction in
effective normal stress. Water may, in addition, cause softening and possible out-wash in the
case of clay-filled joints. It has proved impossible to combine these two parameters in terms
of inter-block effective stress, because paradoxically a high value of effective normal stress
may sometimes signify less stable conditions than a low value, despite the higher shear
strength (Hoek, 2000).
It appears that the rock tunneling quality Q, can now be considered to be a function of only
three parameters which are crude measurments of:
1. Block size (RQD/Jn),
2. Inter-block shear strength (Jr/ Ja), and
3. Active stress (Jw/SRF)
Undoubtedly, there are several other parameters which could be added to improve the
accuracy of the classification system. One of these would be the joint orientation.
If joint orientations had been included the classification would have been less general, and its
essential simplicity lost. Table. 3.5 gives the classification of individual parameters used to
obtain the Tunneling Quality Index Q for a rock mass (Hoek, 2000).
In relating the value of the index Q to the stability and support requirements of underground
excavations, Barton et al. (1974) defined an additional parameter which they called the
Equivalent Dimension, De, of the excavation. This dimension is obtained by dividing the
span, diameter or wall height of the excavation by a quantity called the Excavation Support
Ratio, ESR.
12
The value of ESR is related to the intended use of the excavation and to the degree of
security which is demanded of the support system installed to maintain the stability of the
excavation. Barton et al (1974) suggest the following values shown in Table 3.6.
The equivalent dimension, De, plotted against the value of Q, is used to define a number of
support categories in a chart introduced by Barton et al (1974). This chart has been updated
by Grimstad and Barton (1993) to reflect the increasing use of steel fibre reinforced shotcrete
in underground excavation support (Figure 3.2).
Barton et al (1980) provide additional information on rockbolt length, maximum unsupported
spans and roof support pressure to supplement the support recommendations published in
1974.
The length, L, of rockbolts can be estimated from the excavation width, B, and the ESR by:
(3.5)
The maximum unsupported span can be estimated from:
Maximum span (unsupported) = 2 ESR. Q 0.4
(3.6)
Based upon analyses of case records, Grimstad and Barton (1993) suggest that the
relationship between the value of Q and the permanent roof support pressure Proof is estimated
as:
(3.7)
Other correlations are:
Pwall = 0.7 Proof
(3.8)
RMR = 9 lnQ + 44 (Bieniawski, 1989)
RMR = 5.9 lnQ + 43 (Rutledge and Preston, 1978)
13
(3.9)
(3.10)
Table 3.5. Classification of individual parameters used in the Tunneling Quality Index Q (after
Barton et al., 1974).
11
Table 3.5. continued.
15
Table 3.5. continued.
Table 3.6. Excavation support ratio – ESR for various excavation categories (Barton et al.,
1974).
A
B
C
D
E
Excavation Category
Temporary mine openings
Permanent mine openings, water tunnels for hydropower (excluding high pressure
penstocks), pilot tunnels, drifts and headings for large excavations.
Storage rooms, water treatment plants, minor road and railway tunnels, surge chambers,
access tunnels.
Power station, major road and railway tunnels, civil defence chambers, portal
intersections.
Underground nuclear power stations, railway station, sports and public facilities,
factories.
16
ESR
3-5
1.6
1.3
1.0
0.8
Figure 3.2. Estimated support categories based on the tunnelling quality index Q (after Grimstad
and Barton, 1993).
2.1.4. Geological Strength Index (GSI)
The geological strength index (GSI) is a system of rock-mass characterization that has
been developed in engineering rock mechanics to meet the need for reliable input data,
particularly those related to rock-mass properties required as inputs into numerical analysis or
closed form solutions for designing tunnels, slopes or foundations in rocks (Hoek, 2000). The
geological character of rock material, together with the visual assessment of the mass it
forms, is used as a direct input to the selection of parameters relevant for the prediction of
rock-mass strength and deformability. This approach enables a rock mass to be considered as
a mechanical continuum without losing the influence geology has on its mechanical
properties. It also provides a field method for characterizing difficult-to-describe rock masses
(Hoek, 2000).
The heart of the GSI classification is the careful engineering geological description of the
rock mass which is essentially qualitative, because it was felt that the numbers associated
with RMR and Q-systems were largely meaningless for weak and heterogeneous rock masses
(Hoek, 2000). Note that the GSI system was never intended as a replacement for RMR or Q
as it has no rock-mass reinforcement or support design capability as its only function is the
estimation of rock-mass properties.
This index is based upon an assessment of the lithology, structure and condition of
discontinuity surfaces in the rock mass and it is estimated from visual examination of the
rock mass exposed in outcrops, in surface excavations such as road cuts and in tunnel face
and borehole cores. The GSI, by combining the two fundamental parameters of the geological
process, the blockiness of the mass and the conditions of discontinuities, respects the main
geological constraints that govern a formation and is thus a geologically sound index that is
simple to apply in the field (Hoek, 2000).
17
Once a GSI ‘‘number’’ has been decided upon, this number is entered into a set of
empirically developed equations to estimate the rock-mass properties which can then be used
as input into some form of numerical analysis or closed-form solution. The index is used in
conjunction with appropriate values for the unconfined compressive strength of the intact
rock σci and the petrographic constant mi, to calculate the mechanical properties of a rock
mass, in particular the compressive strength of the rock mass (σcm) and its deformation
modulus (E). Updated values of mi can be found in Marinos and Hoek (2000) or in the
RocLab program (Hoek, 2000).
The geological strength index (GSI) based on two simple equations which were introduced
by Hoek and Brown (1997) can be calculated indirectly as follows:
For
GSI ≥ 18
RMR ≥ 23
GSI = RMR – 5
For
GSI < 18
GSI = 9ln Q′ + 44
(Q′: Tunnelling Quality Index Q′ = [RQD/Jn]. [Jr/Ja])
(3.11)
(3.12)
(3.13)
Basic procedures are explained in Hoek and Brown (1997) but a more recent refinement
of the empirical equations and the relation between the Hoek–Brown and the Mohr–Coulomb
criteria have been addressed by Hoek et al. (2002) for appropriate ranges of stress
encountered in tunnels and slopes. Attempts to ‘‘quantify’’ the GSI classification to satisfy
the perception that ‘‘engineers are happier with numbers’’ (Sonmez and Ulusay, 1999; Cai et
al. 2004) are interesting but have to be applied with caution.
The quantification processes used are related to the frequency and orientation of
discontinuities and are limited to rock masses in which these numbers can easily be
measured. The quantifications do not work well in tectonically disturbed rock masses in
which the structural fabric has been destroyed. In such rock masses, it is recommended that
the original qualitative approach based on careful visual observations is used (Hoek, 2000).
3.2.4.1. When not to Use GSI
The GSI classification system is based upon the assumption that the rock mass contains a
sufficient number of ‘‘randomly’’ oriented discontinuities such that it behaves as an isotropic
mass. In other words, the behavior of the rock mass is independent of the direction of the
applied loads. Therefore, it is clear that the GSI system should not be applied to those rock
masses in which there is a clearly defined dominant structural orientation. Undisturbed slate
is an example of a rock mass in which the mechanical behavior is highly anisotropic and
which should not be assigned a GSI value based upon the charts presented in Figure 3.3
(Hoek, 2000). However, the Hoek–Brown criterion and the GSI chart can be applied with
caution if the failure of such rock masses is not controlled by their anisotropy (e.g. in the case
of a slope when the dominant structural discontinuity set dips into the slope and failure may
occur through the rock mass). For rock masses with a structure such as that shown in the sixth
(last) row of the GSI chart (Figure 3.3), anisotropy is not a major issue as the difference in the
strength of the rock and that of the discontinuities within it is small (Hoek, 2000).. It is also
inappropriate to assign GSI values to excavated faces in strong hard rock with a few
discontinuities spaced at distances of similar magnitude to the dimensions of the tunnel or
slope under consideration. In such cases the stability of the tunnel or slope will be controlled
by the three dimensional geometry of the intersecting discontinuities and the free faces
created by the excavation. Obviously, the GSI classification does not apply to such cases.
Geological description in the GSI should not only be limited to the visual similarity with the
sketches of the structure of the rock mass as they appear in the charts, but the associated
descriptions must also be read carefully, so that the most suitable structure is chosen. The
18
most appropriate case may well lie at some intermediate point between the limited number of
sketches or descriptions included in the charts (Hoek, 2000).
3.2.4.2. Projection of GSI values into the Ground
Outcrops, excavated slopes, tunnel faces, and borehole cores are the most common
sources of information for the estimation of the GSI value of a rock mass. How should the
numbers estimated from these sources be projected or extrapolated into the rock mass behind
a slope or ahead of a tunnel?
Outcrops are an extremely valuable source of data in the initial stages of a project but they
suffer from the disadvantage that surface relaxation, weathering and/or alteration may have
significantly influenced the appearance of the rock-mass components. This disadvantage can
be overcome (where permissible) by trial trenches but, unless these are machine excavated to
considerable depth, there is no guarantee that the effects of deep weathering will have been
eliminated. Judgment is therefore required in order to allow for these weathering and
alteration effects in assessing the most probable GSI value at the depth of the proposed
excavation (Hoek, 2000).
Excavated slope and tunnel faces are probably the most reliable source of information for
GSI estimates provided that these faces are reasonably close to and in the same rock mass as
the structure under investigation. In hard strong rock masses it is important that an
appropriate allowance be made for damage due to mechanical excavation or blasting. As the
purpose of estimating GSI is to assign properties to the undisturbed rock mass in which a
tunnel or slope is to be excavated, failure to allow for the effects of blast damage when
assessing GSI will result in the assignment of values that are too conservative. Therefore, if
borehole data are absent, it is important that the engineering geologist or geologist attempts to
‘‘look behind’’ the surface damage and try to assign the GSI value on the basis of the
inherent structures in the rock mass. This problem becomes less significant in weak and
tectonically disturbed rock masses as excavation is generally carried out by ‘‘gentle’’
mechanical means and the amount of surface damage is negligible compared to that which
already exists in the rock mass. Borehole cores are the best source of data at depth, but it has
to be recognized that it is necessary to extrapolate the one-dimensional information provided
by the core to the three-dimensional in situ rock mass (Hoek, 2000).
However, this is a problem common to all borehole investigations, and most experienced
engineering geologists are comfortable with this extrapolation process. Multiple boreholes
and inclined boreholes can be of great help in the interpretation of rock-mass characteristics
at depth (Hoek, 2000).
For stability analysis of a slope, the evaluation is based on the rock mass through which it
is anticipated that a potential failure plane could pass. The estimation of GSI values in these
cases requires considerable judgment, particularly when the failure plane could pass through
several zones of different quality. Mean values may not be appropriate in this case. For
tunnels, the index should be assessed for the volume of rock involved in carrying loads, e.g.
for about one diameter around the tunnel in the case of tunnel behavior or more locally in the
case of a structure such as an elephant foot. For particularly sensitive or critical structures,
such as underground powerhouse caverns, the information obtained from the sources
discussed above may not be considered adequate, particularly as the design advances beyond
the preliminary stages. In these cases, the use of small exploration tunnels can be considered
and this method of data gathering will often be found to be highly cost effective (Hoek,
2000).
19
Figure 3.3 provides a visual summary of some of the adjustments discussed in the
previous paragraphs. When direct assessment of depth conditions is not available, upward
adjustment of the GSI value to allow for the effects of surface disturbance, weathering and
alteration are indicated in the upper (white) part of the GSI chart. Obviously, the magnitude
of the shift will vary from case to case and will depend upon the judgment and experience of
the observer. In the lower (shaded) part of the chart, adjustments are not normally required as
the rock mass is already disintegrated or sheared and this damage persists with depth (Hoek,
2000).
Figure 3.3. The General Geological Strength Index (GSI) chart for jointed rock
masses estimates from the geological observations (after Hoek and Brown 1997,
Hoek and Karzulovic, 2000).
3.2.5. Slope Stability
3.2.5.1. Slope Mass Rating (SMR)
The Asmari Formation limestones were classified using the SMR method (Romana, 1985).
This classification is based on the RMR-system, by using an adjustment factor depending on
the relation between the slope and joints and also a factor depending on the excavation
method. The relationship between RMR and SMR is as follows:
SMR = RMRBasic + (F1.F2.F3) + F4
51
(3.14)
Where F1 depend on the parallelism between joints and the strike of the slope face as:
F1 = (1- sin A) 2
(3.15)
A is the angle between the strike of the slope face and strike of the joint. The value of F1
varies from 1.0 (nearly parallel) to 0.15 (when the angle is more than 30°) and the probability
of failure is very low.
Table 3.7. Adjustments rating for joints (Romana, 1993).
P
T
Failure Type
αj- αs
αj-αs-
W
P/T/W
P
W
P/W
T
P
W
T
P/W/T
Very Favourable
Favourable
Fair
Unfavourable
Very Unfavourable
>30°
30°- 20°
20°- 10°
10°- 5°
<5°
180°
αj- αs
F1
ßj
ßj
F2
F2
ßj- ßs
ßj- ßs
ßj+ ßs
F3
0.15
0.4
0.7
0.85
1.0
< 20°
20°- 30°
30°- 35°
35°- 45°
> 45°
0.15
1.0
0.4
1.0
0.7
1.0
0.85
1.0
1.0
1.0
> 10°
10°- 0°
0°
0°- (-10°)
< 10°
< 110°
0
110- 120
-6
> 120
-25
-50
-60
P, plane Failure; T, Toppling Failure; αj, joint dip direction; αs, Slope dip direction; ßj, joint dip; ßs, slope dip
F2 depends on the joint dip angle in planar failure mode, and its value varies from 1.0 (for
joints dipping more than 45°) to 0.15 (for joints dipping less than 20°) and F3 refers to the
relationship between the slope face and joint dips. The value of F3 is based on Bieniawski’s
(1976) figures and the conditions are fair when the slope face and joints are parallel.
Unfavourable conditions occur when the slope dips 10° more than joints.
F4 is the adjustment factor depending on the excavation method (Tables 3.7. and 3.8). As
with most other classification systems, the SMR suggests need for and typt of support and
describes five different classes. The tentative descriptions of SMR classes are shown in Table
3.9.
Table 3.8. Adjustment factor due to method of excavation of slopes (Romana, 1993).
Method
F4
Natural slope
+15
Presplitting
+10
Smooth
Blasting
+8
Blasting or
mechanical
0
Deficient
blasting
-8
Table 3.9. The SMR classes (Romana, 1993).
Class
I
II
SMR
81- 100
61- 80
Description
Very Good
Good
Stability
Completely stable
Stable
Support
None
Occasional
Unstable
Failures
No failures
Some blocks
Planar failure in some joints and
many wedge failures
Planar failure in many joints or big
wedge failures
III
41- 60
Normal
Partially stable
IV
21- 40
Bad
V
0- 20
Very Bad
Completely unstable
Big planar or soil- like
Re- excavation
54
Systematic
Important/
corrective
3.2.5.2. Falling Rock Hazard Index (FRHI)
Falling Rock Hazard Index (FRHI) was developed based on work done earlier at the
Oregon and Washington Department of Transportation of United States (Singh, 2004). FRHI
has been developed for excavations that seem apparently stable, to determine the degree of
dangerous situation to workers and installations in the immediate vicinity of the rock slope
excavation at site. This method described herein considers rock slope parameters (Table
3.10).
Explanation of FRHI parameters:









Face height
The greater the face height, the greater the potential energy of falling rock, and
consequently, the greater the danger to workers in the immediate vicinity.
Face inclination
rocks from a vertical slope free-fall while rocks from a slope angle of 30° to 60°
bounce and roll, rendering greater hazard to workers. Vertical slopes and slopes <30°
are safest in this regard. Slopes of 60° to 75° are worst (Ritchie 1963).
Face irregularities
Pfeiffer and Higgins (1990) claim that interaction of face irregularities with the falling
rock is the most important factor in predicting rock fall behavior. The irregularities, or
launching features. Determine the character of the bounce and the subsequent
volatility of danger.
Rock condition
Rock mass conditions, such as, fractures, dip, dip direction, and discontinuities are a
crucial indication of falling rock hazards. A highly fractured rock face exhibits more
potential for rockfall hazard than a hard, intact rock face. The rock quality designation
(RQD) developed by Deere et al. (1967) can be used for this.
Spacing of discontinuity
The spacing of the discontinuities is an indicator of how the planes of weakness affect
the mechanical properties of the rock mass discontinuity under external force. Hence,
closely linked discontinuities have more effect than isolated discontinuities, allowing
smaller blocks to be easily detached on disturbance.
Block size
The larger the block size of falling rocks the greater the danger to the workers below.
Volume of rockfall
This is a highly visible indicator of the seriousness of falling rock. The more the
amount and weight of falling rock, the worse the hazard. It is worthwhile noting that
falling rock situations where the weight of rocks is above 45.36 kg should be closely
evaluated for loss of structural integrity.
Excavation method
Several rock mass properties are compromised as a result of the excavation method.
These excavation methods open existing discontinuities in the rock face and break the
joint asperities. Excavation methods that cause less damage to the rock face are
preferred over other types.
Duration without remedy
Long periods of exposure of a rock face to the natural elements allow increased
weathering effects to take place. Weathering: can weaken the exposed face and lead to
possible dislodging of rock pieces.
52
Table 3.10. FRHI worksheet (after Singh, 2004).
Falling Rock Hazard Index (FRHI)
1.5m- 4.5 m
1.5 m 2 m = 2
2 m- 3 m = 3
3m–4m=5
4 m – 4.5 m = 6
4.5 m – 7.5 m
4.5 m 5 m = 7
5m–6m=8
6 m – 7.5 m = 9
> 7.5 m
7.5 m – 9 m = 10
> 9 m = 12
90º - 75º or
30º – 35º
90º – 80º = 2
80º – 75º = 3
30º – 35º = 4
35º – 60º
60º – 75º
35º – 40º = 5
40º – 50º = 6
50º – 60º = 7
60º – 65º = 8
65º – 70º = 9
70º – 75º = 10
Occasional
Occasional
Irregularities = 3
Many
Many
Irregularities = 8
Major
Major launching
Features = 11
Massive,moderately
jointed and blocky
Few joints and cracks;
Firm interlock of blocks
between joints = 3
Very blocky,
many fractures
Imperfect interlock
of intact rock
fragments; Many
fractures = 7
100 - 90
90 – 50
50 – 25
Spacing of
discontinuity
Scoring
Very wide
> 0.9 m
> 1.2 m = 0
1.2 m – 0.9 m = 1
Wide
0.9 m – 0.2 m
0.9 m – 0.6 m = 2
0.6 m – 0.3 m = 3
0.3 m – 0.2 m = 4
Close
0.2 m – 0.05 m
0.2 m – 0.15 m = 6
0.15 m – 0.10 m = 7
0.10 m – 0.05 m = 8
Block size of
falling rocks
Scoring
breakdown
< 0.05 m
< 0.025 m = 0
0.025 m – 0.05 m
=1
Face height
Scoring
breakdown
Face inclination
< 1.5 m
< 1.5 m = 1
< 30º or 90º
Scoring
Breakdown
1
Face irregularity
Scoring
breakdown
Few
Clear cut = -1
Rock condition
Scoring
breakdown
Equivalent
RQD, %
Volume of
rockfall
Scoring
breakdown
Excavation
method
Scoring
breakdown
Time factor
w/o remedy
Scoring
breakdown
Rockfall
frequency
Scoring
breakdown
Hard and intact
No joints
or cracks = -1
< 4.54 kg
< 4.54 kg = 1
Control
blasting
None to few
fractures = 1
< 1 day
Remedied
rock face = 0
0.05 m – 0.1 m
0.05 – 0.076 m = 2
0.076 – 0.1 m = 3
4.54 kg – 13.6 kg
4.54 kg – 6.8 kg = 3
6.8 kg – 9.1 kg = 5
9.1 kg – 13.6 kg = 7
Mechanical
excavation
Smooth exca. = – 1
Regular cut; some
fractures = 3
Manual cut = 4
1 day – 1 month
< 1 day = 1
1 day – 5 days = 2
5 days – 10 days = 3
10 days– 1 month = 4
0.1m – 0.2 m
0.1 m – 0. 127 m = 4
0.127m – 0.15m = 5
0.15m – 0.17 m = 6
0.17m – 0.20 m = 7
13.6 kg – 22.7 kg
13.6 kg–15.88 kg = 9
15.88kg –18.14 kg =10
18.14kg – 22.7 kg = 11
Regular blasting
Completely
Crushed = 10
< 25
Very close
< 0.05 m
< 0.05 m = 9
0.2m – 0.3 m
0.20m – 0.23 m = 8
0.23m– 0.25 m = 10
0.25 m – 0.3 m = 12
> 22.7 kg
> 22.7 kg = 12
Poor blasting
Fractures; some
irregularities = 5
Highly fractured;
Very irregular
Rock face = 8
> 4 years or
1 month - 4 months
(> 4 year = 5)
1 month – 2months = 5
2 months- 4 months = 6
> 4 months
Maintained rock
face = 7; Not maintained
rock face = 8
Rare rockfall
Occasional rockfall
No rockfall in natural
condition; rockfalls
when disturbed = 3
Rockfall in natural
condition; Much falls
with disturbance = 6
No rockfall
No rockfal l= 0
Highly fractured
Frequent rockfall
Rockfalls without
disturbance; high
requency = 8
Total Score
 Rockfall frequency
A falling rock problem is evident when site workers observe rocks falling under
natural conditions. The greater the frequency, the more serious the falling rock
hazard.
53
Table 3.11. Rock fall hazard classification (after Singh, 2004)
Rockfall hazard classification
Class
I
II
III
IV
Score range
Fall hazard
0- 20
Minimal risk
21- 40
Low risk
41- 70
Moderate risk
71- 100
High risk
Mitigation
measure
Scaling only;
No netting
Type I
netting
Type II
netting
Type III
netting
3.3. Using Rock Mass Classification Systems
The two most widely used rock mass classifications are Bieniawski's RMR (1976, 1989)
and the Q system by Barton et al's (1974). Both methods incorporate geological, geometric
and design/engineering parameters in arriving at a quantitative value of the rock mass quality.
The similarities between RMR and Q stem from the use of identical, or very similar,
parameters in calculating the final rock mass quality rating. The differences between the
systems lie in the different weightings given to similar parameters and in the use of distinct
parameters in one or the other scheme. RMR uses compressive strength directly while Q only
considers strength as it relates to in situ stress in competent rock. Both schemes deal with the
geology and geometry of the rock mass, but in different ways. Both consider groundwater,
and both include some component of rock material strength. Some estimate of orientation can
be incorporated into the Q system using a guideline presented by Barton et al. (1974). The
main difference between the two systems is the lack of a stress parameter in the RMR system.
When using either of these methods, two approaches can be followed. One is to evaluate the
rock mass specifically for the parameters included in the classification methods; the other is
to accurately characterize the rock mass and then attribute parameter ratings at a later stage
(Hoek, 2000). The latter method is recommended since it gives a full and complete
description of the rock mass which can easily be translated into either classification index. If
rating values alone had been recorded during mapping, it would be almost impossible to carry
out verification studies. In many cases, it is appropriate to give a range of values to each
parameter in a rock mass classification and to evaluate the significance of the final result. The
average value of Q can be used in choosing a basic support system while the range gives an
indication of the possible adjustments which will be required to meet different conditions
encountered during construction (Hoek, 2000).
51
Chapter 4
Geology of the Project Sites
4.1. Introduction
In this chapter, the geological characteristics of the Asmari Formation at the following dam
sites are discussed:
1. Karun-3 Dam, in Khuzestan Province,
2. Karun-4 Dam in Chaharmahal Bakhtyari Province,
3. Marun Dam in Khuzestan Province,
4. Seymareh Dam (Hini Mini) in Ilam Province and
5. Salman Farsi Dam (Ghir) in Fars Province
The Asmari Formation limestone is the main foundation rock mass at all investigated dam
sites (Figure 4.1) and generally consists of cream to light gray limestone, marly limestone,
dolomitic limestone and marlstone with sporadically thin layers of shale. Karstification of
limestone due to aggressive water and warm springs are well developed especially at the dam
sites which are located on the northern flank of anticlines (Seymareh, Marun and Salman
Farsi). The direction of shortening at the region due to tectonic movements are indicated by
white arrows. Shortening directions are derived from all axial planar orientation.
4
1
2
3
5
Figure 4.1. The topographical map of Zagros folded belt and locations of five dam sites.
Seymareh (4), Karun-3 (1), Karun-4 (2), Marun (3) and Salman Farsi (5). The direction of
shortening at the region due to tectonic movements are indicated by white arrows. (Lexicorient
base map, 2001).
55
The petrographic characteristics have been determined from thin section studies from the
systematic sampling of outcrops and boreholes (Appendix 1 to 5). It should be noted that the
lithology shown in lithological columns are according to borehole loggings and surface
investigations of outcrops. The detailed petrographical studies have been carried out based on
Folk (1959) and Dunham (1962) the two most widely used methods of carbonate rock
classification. These classifications are used based on the concept of textural (fabric)
maturity, where the fabric is believed to relate to the energy level during the deposition of
limestone.
The porosity values and porosity types are defined according to Choquette and Pray
(1970) who divided carbonate rocks into three groups of fabric-selective type, non-fabricselective porosity type and the third group may display a fabric control or not.
The detailed petrographical descriptions with related photomicrographs are introduced for all
index layers/ subunits of the Asmari succession. Finally, the lithological columns in each
locality of the research area were introduced based on the above investigations and the
engineering properties of the rock units.
Attention was paid to the lithological distribution of the various rock types, their
engineering properties, the compilation of stratigraphic sections, and to structural geology
including bedding, folds, faults and major joints. Also the extent of rock outcrops was
delineated, fault exposures were inspected and logged to assess the likelihood of current fault
activity.
Discontinuity surveys were performed during different stages with more than 2000
discontinuities such as joints and bedding planes measured and plotted to establish statistical
trends (contour plot, rosette plot, and pole plot of joints on equal area projection Schmidt
net). These data were used to define the stability analysis of rock wedges in excavated tunnels
including the diversion and hydropower tunnels, as well as rock slope stability analysis
especially around the dam structure.
Finally, the direction of shortening (major principal stresses) at each dam site (anticlines) due
to active tectonic movements in the Zagros Mountains was derived from all axial planar
orientations.
56
4.2. Geology of the Karun-3 Dam and Power plant
The Karun-3 dam project is located 28 km east of the town of Izeh in northeast Khuzestan
Province. Its crest elevation is 850 m and the average reservoir elevation is 840 m. This is a
double curvature concrete arch dam, symmetrical in shape about a plane running
approximately parallel to the valley direction. The location and alignment of the dam is
limited by geological and topographical features on both abutments. The subsurface
powerhouse is located downstream from the dam and power tunnels.
The service spillway is a chute spillway located on the right flank. Gated orifices in the dam
wall serve as auxiliary spillways and there is also a crest overflow for emergency conditions.
Other structures consist of upstream and downstream cofferdams and a diversion tunnel
under the right flank. The cofferdams are earth and rock fill structures. The diversion tunnel
is a 350 m long and 15 m diameter excavation. The powerhouse contains eight units with a
total capacity of 2 000 MW (Figures 4.2.1 and 4.2.2).
Power Tunnels
Doshablori F.
Spillway
Diversion Tunnel
Cofferdam
to Izeh Town
Dam body
Keyf Malek Anticline
Access Roads
Figure 4.2.1. The satellite image of Karun-3 dam project and surrounding area before reservoir
impoundment. This project located at 28 km east of Izeh town in Khuzestan Province. Access road of
Dehdez – Izeh can be seen on middle part of picture (Google Earth, European Technology, 2009).
The reservoir is 60 km long with storage volume of 3x109 m3 (Table 4.2.1).
4.2.1. Objectives and benefits of the project
a) Generating annually 4 137 million kWH hydroelectric energy through a 2 000 MW
power plant that can be extended to 3 000 MW (MG co. geological report, 1993).
b) Controlling floods and supplying approximately one billion m3 water for irrigation.
c) Increasing hydroelectric energy of the country by 60% and 2.7% of the total electricity
generated in the country.
d) Approximately 200 million dollars of annual benefit.
57
Keyfe Malek Anticline
Dam body
Asmari F.
Spillway
Access roads
Figure 4.2.2. Karun-3 dam a double curvature concrete arch dam constructed on the Karun River.
.
Table 4.2.1. The technical specifications of the Karun-3 dam and power plant project.
Dam Type
Height from the foundation
Length of the crest
Width of the dam at foundation
Width of the crest
Total volume of the reservoir
Useful volume of the reservoir
Power plant type
Spillway
Discharge capacity of the spillway
Water diversion system
Power of the power plant
Double curvature concrete arch dam
205.0 m
388.0 m
29.0 m
5.50 m
2750 million m3
1500 million m3
underground
Chute, gated orifice types and free
21730 m3/s
U/S dike with the height of 43 m small D/S dike with the height of
32 m/ two diversion tunnels with the completed diameter of 13 m
and the length of 613 m for the first one and the length of 536 m
for the second one.
2000 MW (8 units of 250 MW)
4.2.2. Bedrock Geology of Project Area
A summary of the principal bedrock formations present in the project area is given in
Table 4.2.2. A continuous sequence of sediments from the late Cretaceous period to the
Pliocene stage is represented (Figure 4.2.3 to 4.2.5).
The Lower Asmari Formation is made up of interbedded limestone and marly limestone. The
limestone is generally light grey to light brownish grey, fine to medium grained, strong to
very strong. In general the porosity values are between 1% to 15.7% that imply medium to
extremely porous rocks and has been subdivided into four subunits 4a1, 4a2, 4a3, 4a4.
58
The measured weighted mean RQD is between 50% to 85% which indicates fair to good
quality rock mass.
Table 4.2.2. Bedrock formations present at the Karun-3 dam (after James and Wynd, 1965).
Rock Formation/ Group
Bakhtyari Formation
Agha Jari Formation
Gachsaran Formation
Asmari Formation
Pabdeh Formation
Gurpi Formation
Bangestan Group
KhamiGroup
General Description
Chert and limestone conglomerate,
Sandstone and gritstone
Alternating brownish-grey, calcareous, fossiliferous
sandstone, red marlstone and siltstone
Alternating reddish brown and grey salt, anhydrite,
marlstone, marly limestone,
sandstone, siltstone and shale
Alternating grey limestone, marly limestone
and marlstone, overlying thick bedded fossiliferous
limestone
Alternating marly limestone, shale and marlstone,
overlying shale with minor marly limestone
Purple shale with marly limestone and marl
Grey, thick bedded marly limestone with shale
partings, overlying bituminous shale(Kazhdumi)
Grey brown fossiliferous, thick bedded
limestone
Age
Late Pliocene
Late Miocene to Early
Pliocene
Early Miocene
Oligocene to Early
Miocene
Paleocene to Eocene
Late Cretaceous
Middle Cretaceous
Early Cretaceous
The Upper Asmari Formation consists thin to medium bedded marly limestone, marlstone
and shale. The limestone and marly limestone are strong to very strong. The porosity values
are generally between 1% to 13.8% which indicate medium to extremely high values. The
rock quality is variable with the weighted mean RQD of unit 4b between 31% to 81%, which
indicates poor to good quality rock mass (MG co., Koleini, 2009).
K
Geological Map of
Karun.3 Dam Project
EY
4a4
F
M
E
IN
CL
TI
N
A
4a3
LEGEND
Fault A
K
LE
A
4a4
4b
5a
S
Gypsum, anhyrite
and marl
4a3
4a2
4a4
4b
4a2
S
4a3
4a1
limestone and
marly limestone
4a 3
thickly bedded limestone
and marly limestone
3b
KARUN RIVER
4a2
4a 4
T
3b
4a4
marlstone and shale
4a 2
very thickly bedded
limestone
4a 1
thickly bedded limestone
and marly limestone
3b
Marlstone and
marly limestone and shale
S
4b
DO
4a2
SH
4a3
4a3
AB
RI
LO
T
UL
FA
T
S
0
T
4b
100 m
Scale
Figure 4.2.3. Geological map of the Karun-3 Dam and power plant site (after MG co., 2009).
59
615.0 m
ASMARI FORMATION
Figure 4.2.4. Lithological column of the Asmari Formation in the Karun-3 dam site.
61
LEGEND
Elevation
m
Karun.3 Dam Project
Geological section along dam axis
Left flank
Right flank
5a
1000.0
Gypsum, anhyrite
and marl
950.0
4a3
900.0
4b
marlstone and shale
Crest of Dam
850.0
800.0
4a2
4b
4a 4
limestone and
marly limestone
4a 3
thickly bedded limestone
and marly limestone
4a1
750.0
Power Tunnels
700.0
4a 2
very thickly bedded
limestone
4a 1
thickly bedded limestone
and marly limestone
3b
Marlstone and
marly limestone and shale
3b
650.0
4a4
600.0
Diversion Tunnel
550.0
Zone of fractured rocks
4a3
500.0
0.0
100.0
200.0
300.0
4a2
400.0
4a1
500.0
600.0
700.0
800.0
1000.0
1200.0
Figure 4.2.5. Geological section along Karun-3 Dam axes. The hydropower tunnels (4 circular 15 m, 10 m
in diameter) and the diversion tunnel (15 m in diameter) located on right abutment (after MG co., 2009).
4.2.3. Structural Geology
The dam and powerhouse sites are located on the south-western flank of the northwestsoutheast striking Keyf Malek Anticline (Figures 4.2.2 and 4.2.5). This feature controls the
topography and dominant bedrock structure of the project area. The bedding, which is well
developed, has shallow dip at the crown of the anticline but on the south-western limb, the
dip is steep to the southwest. Regular joint sets are developed and these have consistent
orientations across the project area. The Doshablori Fault strikes in a northwest-southeast
direction and passes within 500 m to the southwest of the damsite. The major seismically
active faults in the study area are presented in Figure 4.2.6.
The Keyf Malek anticline is a simple, box-like structure. It is asymmetrical, with the
south-western limb dipping more steeply than the north-eastern one. The axis of the fold
plunges slightly to the southeast (141°/06°) but, for practical purposes, it may be considered
to be horizontal (MG co., 1993).
The strike and dip of the strata vary only slightly over the dam and powerhouse sites. The
bedding has a fairly flat inclination at the top of the fold, but become rapidly steeper to the
west of the axis where it generally dips 60° to 85° southwest. Mapping indicates that several
strongly developed joint sets characterize the bedrock in the area. The bedding and joint set
orientations are listed below in the order of development from the strongest to least
developed. Poorly developed miscellaneous sets are excluded.
Discontinuity surveys were conducted on both sides of the river. Polar plot of these
discontinuities (1 158 discontinuity planes) also the directions of principal stresses are
presented on Figures 4.2.7; 4.2.8; 4.2.9 and 4.2.10. The strike and dip measurements quoted
above are the ranges of the average measurements from each area. Joint set A is strongly
developed at all locations in the project area. Joint sets B and C are more randomly developed
and are absent at some locations.
64
0
50
100
150
Km
Figure 4.2.6. The major seismically active faults in the study area at the Zagros region. (after
International Institute of Earthquake Engineering and Seismology- Iran, 2003).
Table 4.2.3. Bedding and joint sets orientation at the Karun-3 Dam site (after MG co., 1993).
Minor Surfaces
Continuity (m)
Major Surfaces
Minor Surfaces
5-20
1-3
500
100
126- 148 / 75-82
20-100
1-3
300
3-15
B
130-270/ 12-24
Only one major
Surface mapped
1-20
C
310-338 /30-45
-----
5-10
Discontinuity
Set
Bedding
A
Dip Direction (º)
Spacing (m)
/ Dip-(º)
Major Surfaces
223-234/50-90
300
-----
3-20
5-20
Bedding and joint surfaces are usually planar and rough. Joints are frequently open at
surface, but usually closed at depth, although deep weathering along some joints was
observed in drill core. Most joints exhibit some calcite filling and hematite staining.
Rare to occasional clay coatings have been observed on some joint surfaces. Most joints are
tension fractures which are characteristic of anticlines in the Asmari limestone of the simply
folded zone. Slickensides were observed on joint surfaces in surface exposures and in drill
core samples. Slickensided shear joints comprise 10% to 30% of the measured discontinuities
in survey numbers R1, R2, R3, R7, R12, and L7 near the core of the anticline. Elsewhere,
shear joints are rare and make up only 1% to 6% of the measurements. Exceptions are survey
numbers R6 and R5 near the river downstream from the dam, where 20% of the measured
discontinuities are slickensided shear joints.
62
4.2.3.1. Joint Study
4.2.3.1.1. Direction of Principal Stresses at Karun-3 Damsite
To determine the orientation of the principal stresses at the Karun-3 Dam, the numbers of
93 bedding planes, were measured in both abutments as input data, into Dips©, and the
scatter plot, contour plot, major planes plot and rosette plot were analysed to determine the
direction of principal stresses.
The directions of principal stresses (2D) are as follow:
1: 231°/ 0.0° (max. Principal stress)
2: 321°/ 0.0° (intermediate principal stress)
3: 0.0°/ 90° (min. Principal stress)
The direction of 1 coincides with the direction of shortening in the Zagros Fold thrust belt.
Shortening Direction
Figure 4.2.7. The direction of 1 / Shortening at Karun-3 dam site.
63
A
B
C
Figure 4.2.8. The Stereographic projection of joints at the right flank, A- Contour plot, B- Rosette
plot, and C- Pole plot of joints (Dips©, equal area projection-Schmidt net, lower hemisphere).
61
A
B
C
Figure 4.2.9. The Stereographic projection of joints at the left flank. A- Contour plot, B- Rosette
plot, and C- Pole plot of joints (Dips©, equal area projection-Schmidt net, lower hemisphere).
65
A
B
C
Figure 4.2.10. The Stereographic projection of bedding planes at the Karun-3 dam and
identification of principal stresses that have impressed on dam site. The direction of 1 is
coincident with direction of shortening in the Zagros Folded belt (Dips©, equal area projectionSchmidt net, lower hemisphere).
66
4.2.3.2. Regional Faults
It is likely that many important earthquake-generating faults are present in the basement
rocks, although they do not necessarily have surface expressions. There are however a
number of important surface faults in the site region. These are described in Table 4.2.4.
The only important regional fault along which earthquake activity has been documented is
the Main Recent fault. This fault runs along the northwest boundary of the Khuzestan
Seismotectonic province and is coincident with the Main Zagros thrust fault over most of its
length. The project Definition Report lists seven major earthquakes which occurred along this
fault over the past years. The largest measured event is the magnitude 7.4 Silakhor
earthquake of January 1903 (Berberian, 1976).
Regional thrust and reverse faults shown in Table 4.1.4 have been described by Berberian
(1976). Three of these faults, the Masjed Soleyman Fault, Ramhormoz Fault and an unnamed
fault northeast of Masjed Soleyman, are Quaternary in age. In this study they are assumed to
be seismically active even though no definite recent movement along them has been noted.
Table 4.2.4. Summary of Faults near the Karun-3 dam site (Berberian, 1976).
Name of Fault
Type
General Trend
Age of last
Movement
Length
(km)
Distance from
Site (km)
Ramhormoz F.
Thrust- 20-25deg to
NE
NW-SE
Quaternary
120.0
75.0 SW
Msjed soleman
F.
Unnamed F
Unnamed F.
Thrust 20 deg to NE
NW-SE
Quaternary
65.0
60.0 W
Thrust
Thrust
High angle reverse 5070 deg.NE
Thrust and angle
reverse
Oblique slip with right
lateral motion
Possibly large vertical
movement ,right lateral
NW-SE
NW-SE
Quaternary
Pre-Quaternary
50.0
95.0
50.0 W
17.0 NE
NW-SE
Pre-Quaternary
190.0
35.0 NE
NW-SE
Pre-Quaternary
1300.0
70.0 NE
NW-SE
Quaternary- Recent
1300.0
50.0- 70.0 NE
N-S
Pre-Quaternary
90.0 – 300.0
15.0 W
Unnamed F
Main Zagros F.
Main Recent F.
Behbahan line
The Behbahan line while not proven to be a fault, is considered to have some potential for
seismic activity. It is a 300 km long north-south trending lineament which runs transverse to
the general structural trend of the Zagros Mountains and considered to pass approximately 15
km west of the site. In summary, the Behbahan line is not considered to have any significant
impact on the Karun-3Dam (MG. co., 1993)
4.2.3.3. Local Faults
A number of small faults of lengths varying between 5 to 20 km occur within 20 km of
the site. These faults probably developed during Pliocene- Quaternary time as a result of
folding. Their short length suggests that they are probably not related to deep-seated
basement structures and are not capable of generating large earthquakes even if they are still
active. The most important fault is the Doshablori fault (Figure 4.2.11) which is 10 km long.
This fault passes within 500 m of the left abutment of the dam and has been closely examined
at several locations during the feasibility geology mapping program.
Fault A, which is about 500 m to 1 km long, cuts across the Pabdeh and Asmari limestone in
the northeast side of the anticline, about 200 m upstream from the dam site. The fault strikes
15° and has a near vertical inclination. About 15 to 20 m of relative movement has occurred
and the breccia zone is about 2 m wide at the uphill location and 5 to 7 m wide at the cliff
67
face. Slickensided fractures are abundant within and adjacent to the fault zone and bedding
plane shears have been observed at many locations.
4a3
Doshablori F.
4a2
4a4
4a3
4b
4a2
4a1
4a4
44
Pabdeh F.
4a3
4a2
Figure 4.2.11. Karun-3 Dam and Power plant. The subunits of the Asmari Formation can be seen in
both abutments. The Doshablori Fault strikes in a northwest-southeast direction and passes within 500
m southwest of the dam site.
68
4.3. Geology of the Karun-4 Dam and Power plant
The investigated project is located in Chahar Mahal Bakhtyari Province, 85 km south to
southwest of Shahr kord. The geographical coordinates of the area are 50, 24, 50E and 31,
35 , 53 N. The most suitable access to the dam site is provided by the Izeh-Sharekord
asphalt road about 85 km from Izeh.
The project area has high relief with some elevations at about 4 000 m. One of these
mountains is Kuh Sefid with a height of about 3 100 m and is located near the dam site.
Asmari Formation.
DS. Coffer dam
Spillway
Pabdeh Formation
Power plant
Dam Axis
Diversion Tunnel
Munj F.
Diversion Tunnel
Karun River
Coffer dam
Hydropower Tunnel
Munj River
Figure 4.3.1. The satellite image of Karun-4 dam and power plant project on the Karun River. The dam
site located on the southern flank of the Kuh Sefid Anticline and the foundation rocks is Asmari
Formation limestone related to Oligomiocene in age. The various parts of the project can be observed as
well (Google Earth, European Technology, 2009).
The Karun-4 dam and power plant project are located in the Karun River, almost 5 km
downstream of the confluence Bazoft and Armand rivers in a steep U-shaped valley (about
70º) on the southwestern flank of the Kuh Sefid Anticline. This anticline has a northwestsoutheast trend and is asymmetrical with a steeper south-western flank compared to the
north-eastern one. The dam foundation rocks are of the Asmari and Pabdeh Formations.
Karun-4 is a double curvature concrete arch dam that is under construction. The dam has a
height of 230 m and capacity of 2 190 million cubic metres. To divert the water of the Karun
River during the dam construction, two tunnels in the right flank have been designed. The
lengths of these tunnels are 610 m and 635 m and their excavated diameters are 11 m and
11.5 m respectively (9.5 m after final lining). The cofferdams are earth and rockfill structures.
The spillway is a chute and orifice type, 124 m in length and 80 m high comprise five main
bays located on the right flank (Figures 4.3.1 and 4.3.2).
The surface powerhouse contains four units with a total capacity of 1 000 MW (4 250 MW).
69
Figure 4.3.2. The Karun-4 dam site constructed at the southern flank of the Kuh Sefid Anticline (2006).
4.3.1. Objective and benefits of the project
a) Generating annually 2 107 GWh electric energy
b) Supply water for irrigating agricultural lands.
c) Controlling foods
d) Land reclamation
The general technical specifications of the dam project are shown in Table 4.3.1
Table 4.3.1. The technical specifications of the Karun-4 dam and power plant
project (MG co., 1995- 1997).
Dam Type
Height from the foundation
Length of the crest
Width of the dam at foundation
Width of the crest
Total volume of the reservoir
Power plant type
Capacity of the power plant
Generate
Foundation
Spillway
Double curvature concrete arch dam
230.0 m
440.0 m
37.60.0 m
7.0 m
2190.0 million m3
Ground
4 × 250 MW
2107 GWh/ year electricity energy
Limestone (Asmari Formation)
Chute, orifice types and free
4.3.2. Bedrock Geology of Project Area
Based on the geological map of the region at the project area, there are deposits from
Cretaceous Age to the Present (Figures 1.4, 4.3.3 and 4.3.4). The geological formations in the
project area are summarized in Table 4.3.2 and are as follow:
The Asmari Formation (500 m thickness) constitutes the main dam foundation rocks and
divided into three units. The lower unit comprises limestone, porous limestone, and marly
limestone with some marlstone, generally thick to very thickly bedded and highly karstic.
The measured mean weighted RQD is between 55% to 83% which indicates fair to good
quality rock mass.
The middle unit is located downstream of the dam and comprises alternating limestone,
dolomitic limestone, marly limestone and, marl. Karstification is limited. The weighted mean
RQD is between 53% to 84% which indicates fair to good quality rock mass.
71
The upper part consists alternating limestone (medium to thick layers), marly limestone and
marl with slight karstification. The weighted mean RQD is between 45% to 78% which
indicates poor to good quality rock mass.
Table 4.3.2. Geological formations around the project area.
Unit
No.
8
7
6
Quaternary deposit
Bakhtyari Formation
Agha jari Formation
5
Gachsaran Formation
4
Asmari Formation
3
Pabdeh Formation
2
1
RockFormation /Group
Lithology
Age
River alluvium, colluvium deposits
Massive conglomerate, sandstone
Brownish gray sandstone, red marlstone and siltstone
Alternation of salt, anhydrite, gypsum, marlstone,
marlylimestone, sandstone siltstone, reddish brown
Alternation of fossiliferous light-brownish to grey limestone
with marly limestone and marlstone and dolomitic limestone
Alternation of marly limestone calcareous marl and marlstone
overlying purple shale
Quaternary
Late Pliocene to Pleistocene
Late Miocene to Pliocene
Gurpi Formation
Marly limestone and marlstone
Late Cretaceous
Bangestan group (Ilam,
Sarvak and
Kazhdumi formations)
Thick bedded grey limestone and marly limestone with shale
interbeds, overlying bituminous shale (Kazhdumi Formation)
Upper Cretaceous
Early Miocene
OligoMiocene
Late Paleocene to Oligocene
LEGEND:
Gachsaran Formation
(Gs);
Alternation of salt,
anhydrite, gypsum and
marlstone
Asmari Formation (As);
Limestone, marly
limestone and
marlstone
0
100
200
300
Pabdeh Formation (Pd);
Marlstone and marly
limestone
m
Figure 4.3.3. Geological map of the Karun-4 dam and power plant project in the Zagros
Range of Iran. (after MG. co., 1989).
74
500.0 m
ASMARI FORMATION
Figure 4.3.4. Lithological column of the Asmari Formation at the Karun-4 dam site.
72
4.3.3. Hydrogeological Characteristic of the Dam Location
4.3.3.1. Karst Features, Porosity and Permeability
From a hydrogeological point of view, the permeability of the formation range from
highly permeable to almost impermeable. The geological structure of the region also play an
important role in its hydrogeology. The Ilam and Asmari formations are the most permeable
formations of the region with very high flow springs present due to the influence of tectonic
factors (mainly fracture porosity). The Asmari Formation is vuggy and karstic and has mostly
relatively high permeability. Caves, karst channels, enlarged solution joints, stalagmites and
stalactites can be observed in these carbonate rocks. At the Bazoft branch of the Karun-4 dam
reservoir, there are springs with about 0.1- 3.0 cm/ min emerging from the Asmari Formation.
In general, the porosity condition and permeability specifications at the dam axis are
summarized in Table 4.3.3 and 4.3.4.
The petrographical and field investigations show that there are various types of porosity in
the region but fracture porosity is predominant throughout the Asmari Formation succession
(Figures 4.3.4 and 4.3.5). The fracture porosity constitutes about 40% of total porosity
features. This shows the significant role of compressional tectonic movements that affected
the area.
Table 4.3.3. The range of variation of porosity values classified on a logarithmic scale (Cherenyshev, Dearman,
1991).
Porosity %
Descriptive
terms
< 0.01
Very low
porosity
0.01- 0.1
Low
porosity
0.1- 1.0
Medium
porosity
1.0- 10
High
porosity
> 10
Extremely High
porosity
Table 4.3.4. The porosity (%) and permeability of the Asmari Formation units.
Asmari F. / Unit
Porosity Features
U. Asmari/ As.3
Fracture, Intraparticle
M. Asmari/ As.2
Fracture, Vuggy, Channel
L. Asmari/ As.1
Fracture, Vuggy Intraparticle
Porosity%
0.5- 5.0
Medium to High
1- 7.0
High
1- 15.2
High to Ex. High
Permeability
Impermeable to V. High
Impermeable to V. High
High (locally V. High)
Based on these values grouting will be necessary to reduce the conductivity and porosity of
the dam foundation rocks. This will especially be necessary in the Lower Asmari unit which
is highly karstified.
4.3.3.2. Watertightness of Reservoir
During site investigations, a totall of 14 springs were recognized. The evaluation of spring
data indicates that:
a) With exception of two small springs, all of the springs are located above the reservoir
level which is a positive indication from a reservoir watertightness point of view.
b) 70% of springs originate from the Asmari Formation and is proof of the high water
storage capacity and relatively high permeability in this formation.
c) Springs which originate from Pabdeh, Gachsaran, Agha jari and Bakhtiari formations
have low discharges and some of them may also dry up after few months into the hot
season.
73
The distribution of large karst features in the Asmari Formation is limited and the only
considerable observed cave with dimension about 1543 m is on the left flank of the
reservoir at elevation 1200 m (Figure 4.3.6).
0
0
100 cm
15 cm
0
10 cm
Figure 4.3.5. Some karstic features formed due to dissolution of limestone along
discontinuity surfaces. The discontinuity surfaces mainly constituted by compressional
tectonic movements at the region and then enlarged by water dissolution. The small fibrous
cement, dog tooth calcite crystals and micritic cement overgrowth on vuggs and fractures
surface.
Almost all caves have longitudinal shapes with a general direction parallel to bedding also
along the intersection between bedding and joints. The shape of the channels is circular or
elliptical and the dimensions vary between 30 cm to 100 cm.
71
Kuh Sefid Anti.
Asmari F.
Dam location
Asmari F.
Pabdeh F.
Pabdeh
Reservoir area
F.
Figure 4.3.6. The reservoir area of the Karun-4 dam surrounded partly by the Kuh Sefid Anticline. The
Pabdeh Formation constitutes reservoir bed rock near dam location. This formation lithologically
comprise impervious succession of marlstone and marly limestone (2006).
Distribution of geological formations in the reservoir area is not uniform. The reservoir can
be divided in two parts based on outcrop of formations:
a) From dam site area up to, about 2 km upstream of Armand and Bazoft confluence and
along Armand and up to about 11.5 km along Bazoft River, the bedrock is mostly
composed of the Pabdeh and Gurpi formations,
Asmari Formation outcrops above the reservoir elevation.
b) The second part of the reservoir with its particular bedrock characteristics is
considered from 11.5 km to 20 km upstream. This part of the reservoir is made up of
the Asmari, Gachsaran and Agha Jari formation.
The Pabdeh/ Gurpi (30%- impermeable rocks) and Asmari (29%- permeable) have the most
distribution and Bakhtiari has the lowest distribution.
4.3.4. Structural Geology
The Zagros Mountains are considered as a geosynclinal folded belt which appeared as
synclinal and anticlinal folds due to the Alpine Orogeny during the Pliocene period, with a
general trend of northwest- southeast. Figure 4.3.6 indictaes the situation at the Kuran-4 dam
site.
4.3.4.1. Regional Faults
The Bazoft Fault is about 8 km from the dam site at the nearest point. Its trend is northwestsoutheast and the length is about 28 km. It has a thrust mechanism and dips northeast.
The Khajeh – Anvar Fault with a northwest- southeast trend, about 35 km length and thrust
mechanism, this fault is 13 km from the dam site at the closest point.
Dopolan Fault is a thrust fault with northwest- southeast trend, more than 70 km long and
more than 30 km distant from the dam site.
The Maforon Fault extends in a northwest- southeast trend and is 80 km long and 50 km
away from the dam site at the closest point. It has a thrust mechanism with thrust dip towards
the northeast.
75
4.3.4.2. Local Faults
Generally, 20 faults were identified at the dam centereline of which 11 faults are situated
on the left flank and 9 faults on the right flank. They are mostly reverse or strike slip faults
that show influence of compressional tectonic movement at the dam location (Figures 4.3.8,
4.3.9 and 4.3.10). The local faults and their specifications are listed in Table 4.3.5.
Faults with a length of more than 100 m and 10 m to 60 m displacement (F1, F2, F3, F4
and F15) were observed in the Asmari Formation at the dam axis. The fault zone width varies
between centimetres to 5 m and are filled with brecciated rocks, clay minerals, calcite and
oxidized rock material (iron oxide).
The variations of fault dip and dip direction are between 25 to 85 and 45 to 355
respectively. About 44% of faults have dip directions between 60 to 85 and 56% faults
between 100 to 355.
The stereographic projection of faults at the dam axis are presented in Figure 4.3.11.
Based on stereographic projection of reverse faults the directions of major principal stresses
(2D) are as follows (Figure 4.3.7):
1: 247° / 0.0° (max. principal stress)
2: 337°/ 0.0° (intermediate principal stress)
3: 0.0°/ 90° (min. principal stress)
Shortening Direction
Figure 4.3.7. The direction of 1 / Shortening at Karun-4 dam site.
This coincides with the compressional tectonic regime of the Zagros Folded belt.
76
Table 4.3.5. The faults identifications at the Kaun-4 dam axis.
Fault
No.
F1
F2
F3
F3a
F3b
F3c
F3d
F3e
F4
F4a
F5
F6
F6a
F7
F8
F8a
F9
F10
F10a
F11
F12
F13
F14
F15
F16
F17
F18
F56
F57
F19
F20
Location
50
80
65- 100
140
130
135
40- 65
310
75- 85
70- 100
95- 135
140
40- 70
110- 140
45
45
120
130
135-145
350- 45
65
350- 10
-35- 50
300-310
35- 75
110
75
145
25-30
Fault zone
(m)
1- 2 m
1- 2 m
0.5- 5 m
---1- 2 m
-2- 5 m
0- 15cm
---1- 10cm
--1- 16cm
--5- 50cm
1- 1.5m
10-100cm
-1-2cm
10-50cm
-10-15cm
20-30cm
1.5m
--
147
--
Type
Dipº
DDº
L.Flank
L. Flank
L. Flank
L. Flank
L. Flank
L. Flank
L. Flank
L. Flank
L. Flank
L. Flank
L. Flank
L. Flank
L. Flank
L. Flank
L. Flank
L. Flank
L. Flank
L. Flank
L. Flank
R. Flank
R. Flank
R. Flank
R. Flank
R. Flank
R. Flank
R. Flank
R. Flank
Adit G4
Adit G4
R. Flank
Reverse
Reverse
Reverse
Sinistral
Sinistral
Sinistral
Rev/Dex
Normal
Dextral
Reverse
Sinistral
Sinistral
Reverse
Rev/Dex
Sinistral
Dextral
Sinistral
Strike slip
Sinistral
Rev/Sin
?
Strike slip
--Rev/Sin
Rev/Sin
Rev/Sin
---Sinistral
55
70- 80
35- 55
50
55
60
40
50- 70
80
30- 45
70
45
30-40
40- 55
40- 55
40
40
30
57-60
25-42
35- 45
35-40
-25- 55
15- 20
-45- 55
85
50-60
60-65
L. Flank
Sinistral
55
Covered by talus
----R.Fr,CA,CL
-Breccia
Healded,R.Fr
CL,Breccia
--CL,CA,R.Fr
--R.Fr
-CA
CL,CA,R.Fr
-CA,CL,Marl
-R.Fr,CA,CL
CA&R.Fr
-R.Fr&CA
CL,CA
---
Length
(m)
>100
>100
>100
--->50
30-40
>100
>50
75
60
>100
100
20
50
50
60
40
70
70
345
->100
>25
>90
>85
----
Displacement
(m)
60
60
15-30
2.5
2
1.5
1.5-2
1
10
0.5-1.5
1-3
3-4
0.5-20
4-6
2
1
1
1
-1.5
?
--40-55
3
2-2.5
?
-0.3
100-150
--
--
1.5-2
Gouge
Elevation (m)
LEGEND:
Gachsaran Formation
(Gs);
Alternation of salt,
anhydrite, gypsum and
marlstone
Asmari Formation (As);
Limestone, marly
limestone and
marlstone
Pabdeh Formation (Pd);
Marlstone and marly
limestone
Figure 4.3.8. Engineering geological section of the Karun-4 along Dam axis (after MG co., 2010).
77
Figure 4.3.9. The reverse faults F. 15 and F. 17 (slickenside) at the right flank.
Figure 4.3.10. The small scale repetitious reverse faults due to compression movements
in the Asmari Formation rocks the rigid layer of limestone embedded between two
ductile layers of marlstone (northeastern limb of the Kuh Sefid Anticline).
78
A
B
C
Figure 4.3.11. Stereographic projection of faults which are located on the dam axis of the Karun4. A- Contour plot, B- Major planes plot and C- Rosette plot. (Dips©, equal area projectionSchmidt net, lower hemisphere).
79
4.3.4.3. Joint Study
For the joint study at the Karun-4 dam centerline, 77 joints in the right abutment and 116
joints in the left abutment have been measured (totally 193 joints). Based on the
concentration of discontinuity planes in the stereographic projection (Dips©), the major joint
sets on both abutments are shown in Figures 4.3.12 and 4.3.13.
Almost 47% of total joints are filled with calcite, 45% by calcite- clay and in situ soil and 8%
by other gouge materials.
The bedding plane aperture varies between 2 and 100 mm on the surface and decrease in
depth.
The major joint set orientations in the right flank are:
 Js.1: 036º/ 31º
 Js.2: 128º/ 40º
 Js.3 (Bedding planes): 221º/ 68º
The major joint sets on the left flank are:








Js.1: 128º/ 33º
Js.2: 57º/ 30º
Js.3: 06º/ 21º
Js.8: (Bedding planes): 215º/ 72º
Js.4: 323º/ 31º
Js.5: 291º/ 36º
Js.6: 300º/ 69º
Js.7: 89º/ 66º
The two abutments of the dam have slopes of between 75 to 77 while decrease to 30 at
higher elevations (over 950 m). There seems to be some rock wedge instability on both sides
of the dam foundation, but with consideration of the stereographic projection of joint sets and
their intersection points, internal friction angle (38- 45) and aspect of the slope face, there
are not any unstable rock blocks on both dam abutments.
81
A
B
C
Figure 4.3.12. Stereographic projection of joints (discontinuity distribution) at the right flank of
the Karun-4 dam site. A- Contour plot, B- Scatter plot and Rosette plot (Dips©, equal area
projection-Schmidt net, lower hemisphere).
84
A
B
C
Figure 4.3.13. Stereographic projection of joints (discontinuity distribution) at the left flank of
the Karun-4 dam site. A- Contour plot, B- Scatter plot and Rosette plot (Dips©, equal area
projection-Schmidt net, lower hemisphere).
82
4.4. Geology of the Marun Dam and Power plant
The Marun Dam and Power Plant is situated in the Zagros Mountain Range at Tange
Takab (gorge) approximately 19 km northeast of Behbahan in the Khuzestan Province. The
Marun Dam (rockfill) was constructed on the Marun River and is at 165 m high, the second
highest embankment dam in Iran with a crest length of 345 m. The construction was started
in 1987 and completed in 1999.
The main objectives of this project are to regulate the Marun River and provide a dependable
water resource for irrigation in the four plains of Behbahan, Jayezan, Khalafabad and
Shadegan.
Gachsaran F.
Reservoir area
Asmari F.
Marun Dam
Gachsaran F.
Gachsaran F.
Khaviz Anti.
Pabdeh F.
Gurpi F.
Regulating Dam
to Behbahan
City
Figure 4.4.1. The satellite image of the Marun dam site on the northern flank of the Khaviz Anticline.
The Marun rock fill dam constructed at Tange Takab (gorge) approximately 19 km northeast of
Behbahan in Khuzestan Province of Iran (Google Earth, European Technology, 2009).
At the project area, a stratigraphic sequence from upper Cretaceous to Quaternary time
can be observed. The Asmari Formation rocks of Oligomiocene age form the main dam
foundation and comprise limestone, marly limestone and dolomitic limestone interbedded
with marlstone, dipping at 32º-36º to the northeast. The dam is located on the northeastern
flank of the Khaviz Anticline (35 km long and 8 km wide) which has a northwest-southeast
trend (Figures 4.4.1and 4.4.2).
83
Figure 4.4.2. The Marun rock fill dam constructed on the northern flank of the Khaviz Anticline. The
various parts of dam such as semi underground power plant, spillway, diversion tunnels and access road to
the dam crest can be seen. The closed red lines indicate some important instability with high risk of falling
rock hazard.
4.4.1. Objectives and benefits of the project
a) Generating annually 385 GWh hydroelectric energy by two vertical axis turbines and
two generators.
b) Supply water for irrigating of 55 000 ha of agricultural lands at Behbahan, Jayezan,
Khalafabad and Shadegan.
c) Controlling floods and regulating the Marun River
d) Land reclamation
The general technical specifications of the dam project are listed in Table 4.4.1.
Table 4.4.1. Marun dam and power plant project specifications (after MG co., 1986).
Dam Type
Height from the foundation
Length of the crest
Dam body volume
Total volume of the reservoir
Power plant type
Spillway
Water diversion system
Capacity of the power plant
Rock fill dam with clay core
165.0 m
345.0 m
85863040.0 m3
1200 million m3
Semi underground
Gated spillway- four radial gates combined, ending in a ski jump
U/S and D/S cofferdam and two diversion tunnels with 505 m and 640
m length and 10.7 m, 13 m dia.
145 MW (4 units)
4.4.2. Bedrock Geology of Project Area
Figure 1.4 shows the sedimentary succession from the Upper Cretaceous to Quaternary
age with a summary of the geological formations in Table 4.4.2. The geological formations
are discussed below.
The Asmari Formation constitutes the two flanks of the Khaviz Anticline and comprise
alternating grey to light brown limestone, marly limestone and marlstone, which lies on
fossiliferous thickly bedded limestone. Based on the petrographical analysis, physical and
mechanical properties, the Asmari Formation succession can be divided into three main units
(Figures 4.4.3 and 4.4.4).
81
Table 4.4.2. Geological formations around project area.
Unit
No.
7
Rock Formation /Group
Lithology
Age
Quaternary deposit
River alluvium, colluvium deposits
6
Bakhtyari Formation
Massive conglomerate, sandstone
5
Agha jari Formation
Brownish gray sandstone, red marlstone and siltstone
4
Gachsaran Formation
3
Asmari Formation
2
Pabdeh Formation
1
Gurpi Formation
Alternation of salt, anhydrite, gypsum, marlstone, marly
limestone, sandstone siltstone, reddish brown
Alternation of fossiliferous light-brownish to grey
limestone with marly limestone and marlstone and
dolomitic limestone
Alternation of marly limestone calcareous marl and
marlstone overlying purple shale
Early Miocene
Oligomiocene
Late Paleocene to
Oligocene
Marly limestone and marlstone
Gs
Late Cretaceous
Aj
Storage
Mn
Mn
Gs
As
DA
M
Pb
As
980,000
Quaternary
Late Pliocene to
Pleistocene
Late Miocene to
Pliocene
SIT
E
Qt
Gs
Pb
Qt
As
Pb
Gu
KH
AV
Pb
IZ
ulat
ing
Dam
Ma
run
Reg
Riv
er
As
Pb
AN
TI
CL
IN
E
0.0
As
Gs
Gs
As
As
1100
2200
As
Scale
2,010,000
GEOLOGICAL MAP OF MARUN DAM SITE
LEGEND
Pliocene
Miocene
Aj
Mn
Gs
Agha Jari F.
Mishan F.
Gachsaran F.
Oligocene
Eocene
U.Cret.
As
Pb
Gu
Asmari F.
Pabdeh F.
Gurpi F.
Figure 4.4.3. The geological map of Marun dam and power plant project in the
Zagros Range of Iran. The dam foundation is limestone, marly limestone, marlstone
and dolomitic limestone of the Asmari Formation (after MG co., 2010).
The lower Asmari consists of 180 m massive to thickly bedded, high strength,
microcrystalline limestone and marly limestone with thin intercalations of marl and shale,
light grey to grey in color and is relatively highly karstified. Petrographical analysis shows
high porosity that in some places constitutes 15% of the rock volume.
The middle unit consists of 110 m medium bedded karstified microcrystalline limestone and
marly limestone with frequent thin beds of marlstone. The porosity is relatively high and
reaches up to 11% locally. The microfauna’s components are mainly Foraminifera,
Calcareous Red Algae, Echinoid and Pelecypoda shell fragments.
85
ASMARI FORMATION
370.0 m
The upper unit consists of 80 m medium to thinly bedded limestone, marly limestone and
dolomitic limestone, light grey to yellow in color. Karstification is well developed in the
upper part of the unit.and the porosity values vary between 2% and 5.4%.
Figure 4.4.4. Lithological column of the Asmari Formation at the Marun dam site. The
Asmari Formation consists of 370 m limestone, dolomitic limestone, marly limestone
and divided into three main units.
4.4.3. Hydrogeological Characteristic of the Dam Location
4.4.3.1. Karst Features, Porosity and Permeability
Petrographical studies of samples and field investigation at the Marun Dam showed that
the Asmari Formation is the only formation which has relatively high porosity. The
karstification varies from karstified to highly karstified (Figures 4.4.4 and 4.4.5).
The formation has high potential for water storage due to both porosity and karstification.
Some springs that originate from the Asmari Formation have potable water with a normal
taste but there are also lots of salty and sulfur springs in the region that originate from the
Gachsaran Formation (Fars Group). At 500-1500 m from Godaar Nargoon Village, there are
86
three sulfur springs with 10 to 600 l/m discharge. Some small iron springs with 1-2 l/m
discharge were observed in the Pabdeh Formation.
On surface, there are perpendicular fractures almost 10 m long and 15 – 20 m deep that are
partly filled by Quaternary deposits and observations in exploration galleries and boreholes
also indicate cemented breccias and crystallized minerals inside the fracture zones. These
structures originated from tectonic movements but have been enlarged due to dissolution.
The main part of the reservoir underlain by the Fars Group Formation is composed of
gypsum, sandstone marl, shale and a thin layer of limestone (Figure 4.4.6). Lithologically,
this succession seems impervious, but at the contact with the Asmari and Gachsaran
Formations, at the dam and in the reservoir intense karstification caused both probable
discharge conditions. It should be mentioned that the water from the Fars Group can produce
active solutions which can influence the carbonate rocks of the Asmari Formation and
development of karst zones.
The fracture and fissure densities in the lower unit are low but become more abundant in
the middle and upper parts of the Asmari Formation.
The lower part of Asmari Formation consists of massive to very thickly bedded limestone
with well developed karst features such as cavities and dissolution zones, especially at the
base. The porosity values based on petrographical analysis are high to extremely high and
reduce in some places almost 15% of the rock volume.
The middle part consists of medium bedded microcrystalline limestone, marly limestone and
marlstone with dissolution features. Holes and cavities that are partly filled by calcite and
clayey materials indicate acidic water dissolution. The range variation of porosity values is
high to extremely high and reach in some places in the middle and upper part 9- 11% of the
unit volume.
The upper part of the Asmari Formation consists of 80 m of medium to thinly bedded
limestone and dolomitic limestone. Karstification is relatively widespread especially in the
upper part of the unit. Karstification phenomena on bedding planes and through fracture
zones are well developed. The maximum porosity value reaches 5.4% which relates to high
porosity. At the intersection of the main fractures and some bedding planes, the dissolution of
limestone due to aggressive water is well developed.
In the Tables 4.4.3, 4.4.4 and 4.4.5, the porosity and permeability results of three units of the
Asmari Formation, based on petrographical studies and lugeon tests, are listed. The quantity
and quality criteria for permeability classification are:
Table 4.4.3. The quantity and quality criteria for permeability classification (Lewis et al., 2006).
Permeability
Quantity (Lu)
Quality
0- 3
Non
3- 10
Low
10- 30
Moderate
30- 60
High
> 60
V. High
Table 4.4.4. The range of variation of porosity values classified on a logarithmic scale. (Cherenyshev, Dearman,
1991).
Porosity %
Descriptive
terms
< 0.01
Very low
porosity
0.01- 0.1
Low
porosity
0.1- 1.0
Medium
porosity
1.0- 10
High
porosity
> 10
Extremely High
porosity
Based on hydraulic conductivity, porosity and permeability results, it seems that some water
leakages occure especially in the upper and middle Asmari at the dam foundation and cut-off
curtain. Here the cut-off curtain is suspended in the middle Asmari unit.
The design of the grouting curtain was not modified and this has caused the excessive
leakage after the first impoundment of the reservoir. It was decided to impound the reservoir
during the summer of 1996 for agricultural purposes.
87
Table 4.4.5. The porosity and permeability lavues of the Asmari Formation units.
Asmari F. / Unit
Porosity Features
U. Asmari/ As.3
Vuggy, Fracture
M. Asmari/ As.2
Vuggy, Channel
L. Asmari/ As.1
Vuggy, Channel, Fracture,
0
0.5
0
15 cm
Porosity%
2- 5.4
High
1.4- 11
High
1.6- 14.9
High to Ex. High
Permeability
Moderate to High
Low to Moderate
Low to Moderate
m
0
10 cm
Figure 4.4.5. Some karstic features due to acidic water dissolution in the Asmari
Formation limestone. The porosities mostly seem channel porosity, but in some
places at intersection between bedding planes and discontinuities, karstification is
well developed because of limestone dissolution.
88
With the fuse shell, temporary impoundment became possible to satisfy the agricultural
demand and minimize delay in construction activities at the same time. By March 1997, the
embankment had been constructed to 80% of its final height (165 m).
Figure 4.4.6. The reservoir area of the Marun dam site that situated on northeast flank of the Khaviz
Anticline. The upper Asmari Formation limestone as main dam foundation and evaporite rocks of
Gachsaran Formation that constitute a part of reservoir area can be observed.
Immediately after impoundment, considerable leakage was observed in the pressure tunnel
and efforts to open the stoplogs failed. At the same time an embankment was constructed and
subsequent grouting controlled the leakage in the pressure tunnel. The embankment was
overtopped with increasing water elevation, and considerable leakage of up to 7 m3/sec
occured from weak zones upstream of the plug.
The major flow of approximately 4.5 m3/sec was from two large solution channels and
leakage around the concrete plug. The remaining flow was from the access tunnel and the
grouting adit (2.3 m3/sec). Drain holes in the dam body at the toe were dry.
The rock strata at the site comprise a series of karstic limestones interbedded with water
sensitive marls which dip towards the reservoir. In addition, there are two major joint sets, the
first parallel to the bedding, and the second prependicular to the bedding. The water entered
the fissure system upstream of the plug and passed along the fissures, washed out the marls
interbeds forming large cavities. Water was leaking into all tunnels and the dam, and
prevented entry into some tunnels due to high water flows. It was reported that all springs
received their water from the same fissure. Efforts to control the leakage by grouting failed
due to excessive flows and even chemical grouting appeared to be ineffective in blocking the
flow.
The experience clearly indicates that the limestone Asmari Formation is karstified and a
porous succession with a highly potential for water leakage. This succession is accompanied
by some very weak rock layers such as marlstone which is highly susceptible to erosion
under the high hydraulic pressure of the reservoir.
The water tightness of the dam site and reservoir should be investigated in detail to identify
the karstified zones in the Asmari and Gachsaran Formations in addition to the contact zones
between the two formations.
4.4.4. Tectonic Setting
The pre Quaternary formations from the upper Cretaceous to Pliocene are folded due to
tectonic activities dating fom Plio- Pleistocene times. The main tectonic structures are the
Khaviz and Bangestan Anticlines. The dam site is located on the northeastern flank of the
Khaviz Anticline and the Bangestan Anticline as the northern limit of the reservoir.
89
0
50
100
150
Km
Figure 4.4.7. The major seismically active faults in the study area in the Zagros region. This
map shows the distribution of active faults and demonstrates the relationship between the slip
vectors and compressive axis, obtained from the determination of the focal mechanism of the
earthquakes, and GPS velocities (after International Institute of Earthquake Engineering and
Seismology- Iran, 2003).
The two anticlines are asymmetrical with their axes almost parallel trending northwestsoutheast, which is the typical of the main structural trend in the Zagros Region (Figure
4.4.7). The younger formations in the Fars Group (Mio-Pliocene) have an abnormal position
in the syncline between the Khaviz and Bangestan anticlines. They are extensively eroded
and deformed (folded) due to their flexural and plastic characteristics (mainly evaporites and
marls).
The Asmari Formation in the northeastern part of the reservoir (about 10 km from the dam
location) is thrusted over the Mishan and Bakhtyari Formations due to a thrust fault dipping
to the northeast, which imply high compressional movement in the region. In addition some
small displacements and landslides occurr in the Fars Group succession. These phenomena
may be the main cause of slope instability after impoundment of the reservoir. The Asmari
Formation was also deformed by a high angle reverse fault with a northwest-southeast trend
near the power plant location on the left flank. This fault caused some slope instability such
as rock falls and suspended blocks which have enormous potential of falling (Figure 4.4.8).
The main discontinuity planes in this area are:
a) Bedding planes with azimuth 120º to 125º and dip 30º- 35º to the northeast.
The planes have apertures from millimetres to 15 cm partly filled with clay minerals
and carbonate sediments. The surfaces are wavy and rough and are influenced by slight
weathering and karstification.
91
Bangestan Anti.
Figure 4.4.8. Panoramic view of the Khaviz Anticline and Marun dam location with the main faults and
fracture systems. The Keystone graben caused by extensional process at outer core of anticline during
compressional regime can be observed.
b) Joints trending parallel to sub parallel to the bedding planes.
These joints have azimuths 196º to 215º and dip 40º to 50º in the middle Asmari and 60º
to 75º in the other parts of the Asmari succession. Some of these joints pass through all
three units with small displacement and seem to be small faults. The displacement varies
from 0.7 to 1m. In some places slickensides can also be observed. On surface the
fractures are 10 m in length and 15 m to 20 m deep and are partly filled by Quaternary
deposits. In some localities the infill is composed of brecciated, cemented materials and
recrystallized minerals such as calcite.
Field investigations show that there are not any traces of recent movement along these
surfaces.
c) Secondary joints with azimuth 200º to 210º and 60º to 80º dip to the southwest also
influenced the Asmari strata on surface. These fractures are tight at the surface but open
near the slopes. They are 5 m in length and 5 m deep with apertures between 5 and 15
cm. They are perpendicular to the river valley.
d) Joints with azimuth 290º- 300º and 110º to 120º with dip between 70° to 80°.
A lot of fractures, fissures and small faults with short displacements are present in the Asmari
Formation (Figure 4.4.8).
4.4.4.1. Joint Study
A joint survey including 123 joints was taken on both abutments. A stereographic
projection showing the concentrations of the major joint sets is shown in Figure 4.4.10.
The contour plot, rosette plot and pole plot of the discontinuities (equal area projection, lower
hemisphere) are represented in diagram 4.4.10.
The major joint set specifications on the dam axis are as follow:





Js1 (Bedding planes): 033º/ 34º
Js3: 209º/ 74º
Js4: 296º/ 88º
Js5: 033º/79º
Js6: 207º/54º
94
The surface of the bedding planes is generally rough and wavy and filled with clay
minerals and calcite cement. The apertures of the discontinuities are from millimetres to
between 10 -15 centimetres.
The pattern of joint systems as well as the high angle morphology on both abutments,
especially on the left flank (negative angles) create planar sliding and rock fall hazards
(Figure 4.4.2).
Based on the stereographic projection of bedding plane dip directions on both flanks of the
Khaviz Anticline the direction of major principal stresses (2D) can be calculated as follows
(Figure 4.4.10):
1: 213°/ 0.0° (max. principal stress)
2: 303°/ 0.0° (intermediate principal stress)
3: 0.0°/ 90° (min. principal stress)
.
Shortening Direction
Figure 4.4.9. The direction of 1 / Shortening at Marun dam site.
92
A
B
C
Figure 4.4.10. Stereographic projection of joints at the Marun Dam. A- Contour plot, B- Rosette
plot and C- Pole plot of discontinuities (Dips©, equal area projection-Schmidt net, lower
hemisphere).
93
4.5. Geology of the Seymareh Dam and Power plant
The Seymareh dam and power plant project is constructed in the Seymareh River at the
entrance of the gorge of the Ravandi Anticline. The dam is accessible from the Darreh Shahr–
Ilam main road in the Ilam Province of Iran.
The river valley is U shaped with relatively high cliff angles and locally negative angles in
some cases. The geomorphology is basically controlled by the lithology, tectonic history and
climate of the region. The two flanks of dam have very steep slopes below on elevation of
760 m but decrease to 25 degrees above this elevation. The river bed is about 35 to 40 m in
width that gradually increases down stream of the dam position.
Due to some sliding events (according to the surface and subsurface stratigraphic
investigations we found that 4.5 m landslide/rock fall debris underlying about 28 m of lake
deposits and 5.5 m recent river alluvium that is widespread throughout the upstream area of
Seymareh Dam locality), the direction of river flow changed from northwest-southeast to
northeast southwest near the entrance to the gorge (Figure 4.5.1). The river cuts through the
anticline axis and southern anticline flank and flow northwest- southeast into the Talkhab
Plain and finally converge with the Karkheh River.
(Fars Group)
Gachsaran F.
Seymareh River
Reservoir area
U/S Cofferdam
Ravandi Anti.
Diversion Tunnels
Dam location
Power Tunnel
Gachsaran F.
Asmari F.
Access road
to Darreh Shahr
Figure 4.5.1. Satellite image of the Seymareh dam site on the northern flank of the Ravandi Anticline with a
northwest-southeast trend. The Seymareh concrete arch dam is constructed in the Seymareh river valley
approximately 106 km southeast of Ilam city at Ilam Province of Iran (Google Earth, European Technology
2009).
The dam foundation rocks are the Asmari Formation limestone dipping at 25°- 35° at the
entrance of the gorge (dam axis) and gradually decreasing to 10°- 15° downstream near the
anticline axis. The dam is located on the north- eastern flank of the Ravandi Anticline which
has a northwest- southeast trend and is asymmetrical (Figures 4.5.2 and 4.5.3).
91
The Seymareh dam is a double curvature concrete dam which is presently under construction.
This dam, with a gated spillway, has a height of 180 m and reservoir volume of 3215 m3.
Other structures consist of upstream and downstream cofferdams and two diversion
tunnels at the right flank. The diversion tunnels are 473 m, and 397 m long with 10.5 m and
8.3 m diameter respectively. The cofferdams are earth and rock fill structures.
The powerhouse contains three units with a total capacity of 480 MW that generates
843GWh/year electricity.
(Fars Group)
Power Tunnel
Ravandi Anti.
Gachsaran F.
Dam location
Diversion Tunnels
To Darreh Shahr
U/S Cofferdam
Access roads
Asmari F.
Seymareh River
Gachsaran F.
Figure 4.5.2. Aerial view of Seymareh dam site being constructed on the northern flank of the
Ravandi Anticline (after khoshboresh, 2007).
4.5.1. Objective and benefits of the project
a) Generating annually 843 million kWh hydroelectric energy via three units’ power
plant.
b) Supply water for irrigation of agricultural lands.
c) Controlling flooding in the Seymareh River.
d) Land reclamation
e) Approximately 40 million dollars of annual income due to electricity generated by this
project
The general technical specifications of the dam project are summarized in Table 4.5.1.
95
Right Abut.
Left Abut.
Dam crest
Spillway
Manuran Anti.
Downstream
Cofferdam
Diversion Tunnel
2
Down
stream
Figure 4.5.3. The Seymareh dam foundation rocks and associated structures such as diversion
tunnels, spillway and downstream cofferdam. The dam foundation rock is Asmari Formation
limestone (2007).
Table 4.5.1. The technical specifications of the Seymareh dam and power plant project.
Dam Type
Height from the foundation
Length of the crest
Dam body volume
Total volume of the reservoir
Power plant type
Spillway
Water diversion system
Capacity of the power plant
Double curvature concrete type
180.0 m
202.0 m
500,000 m3
3215 million m3
Ground, 2.5 km down stream
1-Gated spillway, 2- Free on dam body
U/S and D/S cofferdam and two diversion tunnel with
473 m, 397 m long and 10.5m, 8.3 m. diameters
480 MW (3 units of 160 MW)
4.5.2. Bedrock Geology of Project Area
Based on the geological map of the region at the project area, there are deposits from
Oligocene to Quaternary Era (Figure 1.4). The geological formations in the project area are
summarized in Table 4.5.2.
The Asmari Formation as the main foundation rocks is divided into three units;
The lower unit lithologically comprises 188 m medium bedded, fossiliferous marly limestone
and microcrystalline limestone. The porosity varies between 1.4% to 5.2% that indicates a
high porosity index. The rock quality designation (RQD) is about 80% which indicates good
quality rock mass. The permeability values vary from non to medium permeability for this
unit. The uniaxial compressive strength (UCS), based on Schmidt hammer field tests and
laboratory tests is about 95 MPa.
96
The middle unit lithologically comprises 238 m massive to thickly bedded, crystalline
limestone, dolomitic limestone and marly limestone light to dark grey in colour. Except for
the first part of the diversion tunnels, all dam structures are constructed in this unit.
Karstification features can be observed throughout the unit. The porosity value in the lower
part is 7.5% which implies high porosity and decrease gradually to 0.95% in the upper part.
The permeability, based on lugeon test results, indicates low to high values (Figure 4.5.5).
The UCS and RQD are 70-100 MPa and 75%- 95% (good quality) respectively.
LEGEND:
U.Asmari (As.3);
Medium to thin bedded microcrystalline
limestone and marlylimestone
M.Asmari (As.2);
Massive to thickly bedded crystalline
limestone, dolomite and marly limestone
L. Asmari (As.1);
Medium bedded limestone, marlylimestone
0
500 1000 1500
m
Figure 4.5.4. The engineering geological map of the Seymareh dam and power plant project. Asmari
Formation constitutes the dam foundation rocks and comprise grey to light grey limestone, dolomitic
limestone and marly limestone Oligomiocene age (after MG co., 2010).
Table 4.5.2. The geological formations at the Seymareh dam site.
Unit
No.
4
3
Rock Formation/ Group
Lithology
Quaternary deposit
River alluvium, colluvium deposits
Bakhtiary Formation
Unconformably massive
conglomerate and sandstone
Alternation of salt, anhydrite, gypsum, marlstone,
marlylimestone, sandstone siltstone, reddish brown
2
Gachsaran Formation
1
Asmari Formation
Cream to brown limestone, marly limestone
dolomitic limestone and marl, fossiliferous
97
Age
Quaternary
Late Pliocene to Pleistocene
Early Miocene
OligoMiocene
572.0 m
ASMARI FORMATION
Figure 4.5.5. Lithological column of the Asmari Formation at the Seymareh dam site. The
Asmari Formation consists of 572 m cream to light grey limestone, dolomitic limestone,
marly limestone and marlstone which is divided into three main units.
98
The upper unit lithologically comprises 150 m grey to dark grey microcrystalline limestone,
bioclastic limestone and marly limestone, karstified and medium to thinly bedded (Figure
4.5.5).
The porosity values are between 0.75% to 4.4% that indicate medium to high porosity. The
permeability is high to very high. The UCS and RQD values based on laboratory tests are 60100 MPa and 65%- 94% (fair to good quality) respectively.
4.5.3. Hydrogeological Characteristics of the Dam Location
4.5.3.1. Karst Features, Porosity and Permeability
The hydrogeology at the dam site includes formations with very high permeability to
almost impermeable. The limestone rocks of the Asmari Formation are the most susceptible
to dissolution and karstification.
The main factors influencing the permeability of the rocks are the occurrence of joints and
fractures due to tectonic movements and this can intensify karstification. Tectonic activities
can cause extensive joint systems along water which can flow through the rock mass. The
joints play a main role in the development of karstification. These joints constitute a
continuous path for movement of mineral waters causing dissolution and karstification.
The most important features are extensional joints caused by high shear stress on bedding
planes. These joints constitute a continuous path for water flow and the extension of
karstification.
Exploratory drilling results and lugeon tests (dam axis) indicate that the permeability near
the fault zones show relatively high values. For example in borehole HM23 and HM12 on the
right flank, the average permeability is 6 and 31 lugeon respectively, but in boreholes HM15
and HM16 which are located near the crushed zones the permeability values are very high.
On the left flank in boreholes HM5 and HM22 permeability are 12 and 48 lugeon
respectively which indicate moderate to high permeability and for the river section the values
are 10 to 23 lugeon.
In general, the permeability conditions of the three units are as follows:
 Upper Asmari between 30 to 74.4 lugeon
 Middle Asmari between 4 to 45 lugeon
 Lower Asmari between < 1 to 19 lugeon
Petrographical analysis and field investigations indicated that the cavities can be divided into
two types:
 Cavities due to dissolution and karstification processes (secondary process).
The diameter of the cavities generally vary from 10 - 150 cm and reach tens of metres
downstream partly filled by clay minerals and calcite. These cavities have been
caused by extensive dissolution of limestone through discontinuity surfaces such as
joint sets and bedding planes especially at their intersections (Figure 4.5.6 and Figure
4.5.7.A, B).
 Cavities due to diagenetic processes.
These cavities generally are circular and elliptical shapes with maximum diameter of
10 cm and constitute maximum of 7.5% of total volume of rocks, partly filled by
calcite cement. It seems not to have any hydrogeological connection with each other
(Figure 4.5.7.B, C).
99
There is a cavity 30 m long, 7 m width, and 10 m deep 600 m downstream of the ancitlinal
axis in the Kaffeh Nila Gorge. Recent exploratory drilling (by MG. co., 2007) also indicated
a large karst cavity in the lower Asmari unit underneath the river bed which had not been
observed during phases 1 and 2 of the investigations. These karst features were caused by
extensive dissolution activities of acidic water through the Asmari limestone succession.
In general, there are a lot of springs in the area between the dam site and Iron Bridge near the
Talkhab Village that are obviously related to fracture systems and enlarged bedding planes
due to dissolution. The discharge values vary between less than 1 l/sec for the seasonal
springs to a maximum of 140 l/sec for non seasonal springs. The water temperature is 19°20° and has a constant temperature throughout the year.
The hydrochemical analysis of spring water indicates high calcium sulphate and sodium
chloride content.
Spillway
Dam crest
Right
Abut.
Left
Abut.
Dam body
Cavities
Cavities
Figure 4.5.6. The large cavities due to dissolution of limestone mainly along bedding planes downstream
of the dam axis. These features can be observed high on both flanks of the dam foundation (2007).
Dye tests have been carried out to determine the hydrogeological connection between the
Gachsaran and Asmari formations but apparently any dye traces have been observed in the
Asmari Formation rocks. The hydrochemical analyses of spring waters in the down stream
indicate high calcium sulphate and sodium chloride which imply hydraulic connection
between the two formations. Future exploratory investigations to identify the hydrogeological
conditions at the dam location and in the reservoir area will be necessary.
411
A
0
100 cm
B
0
C
30 cm
0
20 cm
Figure 4.5.7. Some karstic features related to dissolution of limestone through discontinuity surfaces
by aggressive water with dimensions from 10 cm to metres (A, B) and cavities related to diagenetic
process with small dimensions (B, C).
414
4.5.4. Tectonic Setting
4.5.4.1. Regional Tectonic
The Seymareh dam site and its reservoir are located in the tectonic province of southwestern Iran, the Zagros folded belt (Figure 4.5.8). The dam is constructed on the northern
flank of the Ravandi Anticline (Figure 4.5.9) which is an asymmetrical and double plunging
fold where is the northern flank dips have shallower gradient than the southern one (25°30°). The Ravandi Anticline, with a northwest- southeast trend, follows the general trend of
the Zagros Mountains. Satellite images indicate variable strike due to tectonic stresses. At the
dam axis it is about east- west in the southern part it is N123°E and in the northern part the
strike changes to N115°E. The anticline layers comprise the Asmari Formation limestone that
dips 25°- 30° northeast at the dam axis. The dip of the bedding planes in the upstream part
increases to 50° based on exploratory drilling and in the downstream it gradually decrease
and finally reaches to about 0° (horizontal) near the anticline axis. The southern flank of the
anticline shows more regular dip at the bedding than the northern flank.
0
50
100
150 Km
Figure 4.5.8. The major seismically active faults in the study area in the Zagros region. This map
shows the distribution of active faults and demonstrates the relationship between the slip vectors and
compressive axis obtained from the solution of the focal mechanism of the earthquakes, and GPS
velocities (after International Institute of Earthquake Engineering and Seismology- Iran, 2003).
The reservoir area is limited by the Ravandi Anticline on the southern rim and the
Manuran Anticline on the northern rim. The Manuran Anticline is also an asymmetrically
folded structure which axis follows the Zagros Mountains that are relatively parallel to each
other. The azimuth of the Manuran Anticline axis is about N104°E. The other important fold
structure which is situated between the two main folds is the Buneh Har Anticline with axis
trending N107°E.
Related to these fold structures, are parasitic folding due to compressional stresses in syncline
between the two fold structures. The Fars Group, especially the Gachsaran Formation with
412
plastic and solubile characteristics was extensively subjected to small scale folding and
faulting. This cause a major problem for watertightness in the reservoir.
4.5.4.2. Small Scale Faults and Direction of Principal Stresses at the Seymareh Dam site
A total of 16 faults have been recognized at the dam site. They are generally classified as
reverse and normal faults. The reverse faults are mainly situated at the dam axis and the
normal types are mainly in the area around the anticline axis. Due to compressional stress,
which is the main factor causing the reverse faults, an extensional area is created at the top of
the anticline and the normal faults took place due to gravity processes (Figure 4.5.10).
The identified faults can be divided into two groups;
a) Vertical to very steep faults
These faults with small displacements of between 0.5 to 1 m are mostly observed in
the area between the anticline axis and dam axis. These faults have not significantly
influenced the geomorphology of the area due to small displacements and constitute
the small scale key stone graben in the area around the anticline axis. The structures
were caused by gravitational processes (Figures 4.5.9 and 4.5.10).
The only fault, F10, with a brecciated zone of 0.5 to 2 m wide occurs at the dam axis.
Figure 4.5.9. Panoramic view of the Seymareh river valley at the Ravandi Anticline with the Seymareh dam
location on the northern flank of the anticline. The reservoir with 3 215 million cubic metres volume and
upstream cofferdam as well as the Manuran Anticline are also shows.
All faults have a trend of between W-E to N-S. In some places faults have displacements of
20 to 30 cm.
b) Oblique faults
These faults with 45° to 70° dip are commonly reverse faults and can be observed
around the dam axis (Faults no. F10, F7, F4 and F1) with dips of 70°, 45°, 65° and
45° respectively. Their strike is relatively parallel to the bedding planes (Figure
4.5.11). These faults with small displacements also appear toward the anticline axis
and generally belong to the extensional- gravitational processes (normal faults).
413
Figure 4.5.10. Small scale normal faults (key stone graben) on the right side of the Seymareh River
valley. These structures occurr in the area around the anticline axis where extensional area was
created at the top, then followed by vertical displacement of blocks due to gravity.
Elevation (m)
LEGEND:
0
50
100
150
m
U.Asmari (As.3);
Medium to thin bedded
microcrystalline limestone
and marlylimestone
M.Asmari (As.2);
Massive to thickly bedded
crystalline limestone,
dolomite and marly
limestone
L. Asmari (As.1);
Medium bedded limestone,
marlylimestone
Figure 4.5.11. The engineering geological cross section of the Asmari Formation along the dam axis.
The Asmari limestone units were subjected to faulting and folding due to compressional stresses. The
faults are mainly reverse faults with small displacements. The exploratory boreholes BH5, BH7, BH9,
BH10, BH33 and BH34 indicate the RQD and permeability values of the rock mass (after MG co.,
2009).
411
A
B
C
Figure 4.5.12. Stereographic projection of faults (general orientation of small- scale faults) at the
two abutments of dam site A- Contour plot, B- Rosette plot, and C- Pole plot of faults with field
stress directions (Dips©, equal area projection-Schmidt net, lower hemisphere).
415
Figure 4.5.11 shows the engineering and structural geology at the dam axis. The three
units of the Asmari Formation are completely influenced by the 14 faults with hidden faults
which are covered by relatively thick river alluvium deposits (~50 m).
In Figure 4.4.12 the stereographic projection of faults including contour plot, rosette plot and
scatter plot in Dips©. These plots are based on the poles concentration. The field stress in 2D,
are identified as follows (Figure 4.5.13):
1: 191°/ 0.0° (max. principal stress)
2: 281°/ 0.0° (intermediate principal stress)
3: 0.0°/ 90° (min. principal stress)
Shortening Direction
Figure 4.5.13. The direction of 1 / Shortening at Seymareh dam site.
4.5.4.3. Joint Study
A total of 89 joints from the two abutments of dam the have been measured and presented
contour plot, rosette plot and pole plot of joints (Figure 4.5.14). Based on the stereographic
projection of joints in Figure 4.5.14 excluding the bedding planes another three joint sets can
be identified at the dam location were Js.1, Js.2 the main joint sets and the Js.3 is an
accessory joint set.
The bedding planes and joint sets have the following orientations:




Js.1 170º- 175º/ 65º- 75º
Js.2 270º- 275º/ 80º- 90º
Js.3 120º- 130/ 70º- 80º
Bedding planes 10º- 20º/ 25º- 35º
The average lengths of the Joint sets are:
 Js.1 More than 10 m
 Js.2 3- 10 m
 Js.3 1- 3 m
The discontinuity surfaces are rough and wavy with apertures of less than 2 mm.
Discontinuity fillings are mostly calcite, clay minerals and rare detrital materials but in some
places joints without any fill materials can be observed. Iron oxides commonly stain
416
discontinuity surfaces without any fill. The spacing of Js.1, Js.2 and Js.3 are 55, 65 and 140
cm respectively.
It can be assumed that the joints Js.1 and Js.2 are extensional with Js.3 a shear joint if the
orientation of the anticlinal axes and field stress directions are taken into account. The
azimuth of Js.1is parallel and the Js.2 prependicular to the anticline axis.
An important technical problem is the instability of rock blocks from upper Asmari unit on
the northern flank of the Ravandi Anticline around the dam location. At an elevation between
620 to 800 m, there is an area of 250 m x 300 m which is covered by unstable blocks due to
the intersection of Js.1, Js.2 and bedding planes on the left flank (200 m east of the dam axis).
On the basis of the stereographic projection of joint sets (Figure 4.5.15), the bedding planes
will be the main rock sliding surface for all blocks, if failure takes place (planar failure). The
thickness of the sliding zone is estimated to be 20 to 25 m.
Such blocks formed by the same structures can be observed on the right side of the
northern flank of the Ravandi Anticline. The satellite image of the dam site (Figures 4.5.1 and
4.5.2) shows a sudden change in the river flow direction from northwest- southeast (N120°E)
parallel with anticline axis, to northeast-southwest (N56°E), which constitutes a sharp river
meander about 500 to 600 m from the dam location. This structure was most probably caused
by a huge landslide of the right flank in historic times (exploratory drilling investigation
indicates 4.5 m slope wash debris including fine materials to angular boulders of limestone
and rockfall debris underlie 28 m silty clay of lacustrine deposites).
Consideration of structural evidence mentioned above and seismic data, the sliding
phenomena is expected on the northern flank of the anticline where the inlets of the diversion
tunnels and hydropower tunnel structures may be at risk. Water overtopping due to a huge
landslide after impoundment should also be considered.
417
A
B
C
Figure 4.5.14. Stereographic projection of joints (discontinuities distribution) at Seymareh dam site
A- Contour plot, B- Rosette plot, and C- Pole plot of joints (Dips©, equal area projection-Schmidt
net, lower hemisphere).
418
4.6. Geology of the Salman Farsi Dam and Power plant
The Salman Farsi dam project is located at the entrance of the Karzin Gorge in the Ghareh
Agahaj River, about 140 km south of Shiraz city and 12 km northeast of Ghir Town in the so
called folded foothills belt of the Zagros Mountains. This tectonic province in southern Iran is
characterized by a simple folded sedimentary sequence, of which only post Permian and
younger than Oligocene to Pliocene rocks are exposed (Figure 4.6.1).
In the project area, the stratigraphic sequences are of the upper Cretaceous to the Present. The
dam foundation rocks are of the Asmari Formation of the Oligomiocene and generally
comprise limestone, marly limestone, dolomitic limestone and marlstone.
(Salt dome)
Dareh Siah F.
Ghir F.
Figure 4.6.1. Satellite image of the Salman Farsi dam site and surrounding area on the northern flank of
the Changal Anticline (Google Earth, European Technology 2006).
The dam with a gated spillway is 125 m high and has a capacity of 1 400 million m3. The
spillway contains three main bays with eight combined radial gates, ending in a ski jump
(Figure 4.6.2).
Other structures consist of upstream and downstream cofferdams and a diversion tunnel in
the left flank. The cofferdams are earth and rockfill structures and the diversion tunnel is
about 375 m long and 15 m in diameter. The powerhouse contains two small units with a total
capacity of 13MW (26.5MW) that will generate 50 GWh/year.
4.6.1. Objective and benefits of the project
a) Generating annually 50 million kWh hydroelectric energy via a 13MW power plant.
b) Supply water for irrigating 32 000 ha of agricultural lands.
c) Controlling floods.
d) Land reclamation
The general technical specifications of the dam project can be observed in Table 4.6.1.
419
Changal Anticline.
Karbasi Anticline
Reservoir area
Figure 4.6.2. Salman Farsi (Ghir) dam is a concrete arch gravity dam 125 m high and is under
construction on the Ghareh Agahaj River.
Table 4.6.1. Salman Farsi dam and power plant project specifications.
Dam type
Height from the foundation
Length of the crest
Dam body volume
Total volume of the reservoir
Power plant type
Spillway
Water diversion system
Capacity of the power plant
Concrete arch gravity
125.0 m
345.0 m
750,000 m3
1400 million m3
Ground
Gated spillway- eight radial gates combined, endingin
a ski jump
U/S and D/S cofferdam and a diversion tunnel with
375m long and 15m. diameter
13MW (2 units of 6.5MW)
4.6.2. Bedrock Geology of Project Area
A summary of the principal bedrock formations present in the project area is given in
Table 4.6.2. At the project area, a continuous stratigraphic sequence of sediments from the
upper Cretaceous period (K) to the Pliocene (N) stage are present with a salt dome of the
Hurmoz Formation of Precambrian age intruded to the upper strata (Figure 1.4).
The Asmari Formation in the study area is divided into three units:
The Asmari Formation divisions are according to their engineering and petrographical
properties (Figures 4.6.3 and 4.6.4).
441
Table 4.6.2. A summary of the principal formations in the project area.
Unit No.
8
7
6
Rock Formation/ Group
Quaternary deposit
Bakhtiary Formation
Agha Jari Formation
5
Mishan Formation
4
Razak Formation
3
Asmari Formation
2
Pabdeh Formations
1
Gurpi Formations
Lithology
River alluvium, colluvium deposits
conglomerate and sandstone
Calcareous sandstone, red marls
and siltstone
Grey marl and shelly limestone
Alternating red shale and siltstone with
marl and gypsum
Age
Quaternary
Plio- Pleistocene
Late Miocene to
Pliocene
Early to M.Miocene
Early Miocene
Cream to brown limestone, marly limestone
dolomitic limestone and marl, fossiliferous
OligoMiocene
Cherty, fossiliferous limestone, marly
limestone, shale
Bluish grey marl and shale
Late Paleocene to
Oligocene
Late Cretaceous
The lower Asmari is about 230 m thick and is situated downstream of the dam site and
lithologically, comprises regularly bedded fined grained, brown limestone and marls.
Geological Map of
Razak F.
Salman Farsi Dam
Gravity-Arch Dam
U.Asmari
Legend:
Diversion Tunnel
Razak Formation
Red shale and siltstone with marl
and gypsum
M.Asmari
Asmari Formation
U.Asmari;
Thin bedded of shelly Limeston
and marly limestone
M.Asmari;
Thick bedded of crystaline
limestone and marly limestone
L.Asmari;
Thick bedded of crystaline
limestone karstified,
thin bedded of marl
Ghareh Aghaj
River
L.Asmari
Pabdeh Formation
Shale, marl and marly limestone
Scale:
0
50
100
150
200 m
Pabdeh F.
Figure 4.6.3. Simplified geological map of the Salman Farsi dam and power plant project. Several
small-scale strike slip faults. (after MG co., 2009).
The middle Asmari comprises 270 m heterogeneous and thickly bedded crystalline
limestone, dolomite, and dolomitic limestone with some rare marly limestone interbeds. The
dam and grout curtain are situated in this unit. Karst features are well developed.
The upper unit outcrops upstream of the dam axis and form the eastern and western
reservoir flanks immediately upstream of the dam site. This unit comprises, alternating thinly
bedded limestone, marl and marly limestone with some thin dolomitic limestone and siltstone
interbeds. It is less permeable than the Middle and Lower units. The thickness of the unit is
about 150 m.
444
650.0 m
ASMARI FORMATION
Figure 4.6.4. Lithological column of the Asmari Formation and petrographic analysis
interpretations at Salman Farsi (Ghir) dam.
442
4.6.3. Hydrogeological Characteristic of the Dam Location
4.6.3.1. Karst Features and Porosity
Most of the rocks exposed at the dam site show secondary porosity such as vuggy,
channel, cavern and fracture features. The bedding planes and other discontinuities are also
enlarged by dissolution of limestone and well developed karstification especially in the
middle unit of the Asmari Formation rocks (Figure 4.6.5). Primary porosity due to an
incomplete diagenetic recrystallization and compaction can also be observed locally.
Based on field observations and petrographical studies the lower unit has isolated cavities and
the porosity reaches a maximum of 5.6% locally (lower most part of the unit).
0
0.5
0
1.0m
0
0.5
1.0
2.0m
1.0m
Figure 4.6.5. Some karstic features due to dissolution of limestone along discontinuity surfaces in
the upper part of the middle unit of the Asmari Formation. These features constitute a 3D network of
channels, which somewhere converge into huge caverns.
443
Elevation (m)
SIMPLIFIED GEOLOGICAL SECTION ALONG
GROUT CURTAIN AND GROUTING GALLERIES
Left Bank
950.0
900.0
M.Asmari
1GL
850.0
3GL
800.0
L.Asmari
750.0
5GL
700.0
Diversion Tunnel
Limit of Grout Curtain
650.0
600.0
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
Elevation (m)
SIMPLIFIED GEOLOGICAL SECTION ALONG
GROUT CURTAIN AND GROUTING GALLERIES
Right Bank
1100.0
1050.0
M.Asmari
1000.0
950.0
L.Asmari
1GR
900.0
2GR
850.0
3GR
4GR
800.0
Legend:
U. As.: thinly bedded
limeston and marl
M. As.: Thick bedded of
limestone and dolomitic
limestone
L.As.Thin to v.thin bedded
of limestone and marl
0.0
100.0
750.0
700.0
Limit of Grout Curtain
650.0
200.0
300.0
400.0
500.0
600.0
700.0
Figure 4.6.6. The engineering geological section of the Asmari Formation at the right and left
flanks of the Salman Farsi dam. The exploration and grouting galleries, limit of cut-off curtain and
section of diversion tunnel can be observed (after MG co., 2009).
In the middle unit, karstification is well developed with the largest karst zones present in
the upper part of the unit, whereas karst features are seldom seen in the lower part. The
petrographic analyses show the general porosity reaching a maximum of 8.0% in the upper
part of the unit. Chimneys and karsts are extensively developed on the intersection of bedding
planes and joints and are due to water dissolution (Figure 4.6.5).
Except for the lower most part of the unit, the karst features in the upper unit are restricted.
The porosity comprises very small cavities that follow the limestone bedding planes and
joints. In the upper most part of the unit where the Asmari Formation locally is thrusted on to
the Razak Formation, the crushed zone shows high porosity that was gradually increased due
441
to infiltrating meteoric water (epigenic karst) and hydrothermal waters (hypogenic karst)
(Klimchouk, 2007).
Three factors caused the development of karst; the lithology, distribution of rock type, and
the occurrence of discontinuities. From the lithological point of view, there is a general
tendency for strong dissolution of the porous, vuggy, micritic limestone compared to the
more resistant, less porous, recrystalized, finely to medium-grained calcarenite. Fossiliferous
and finely grained cherty limestone of the middle unit is rarely showing weathering, whereas
marls and marly limestones are impervious. Observations through exploration galleries
clearly show that the cavities are initiated at the intersections of the bedding and joints and
enlarged along the bedding planes.
The general shape of the karst features results in metres long oblate chimneys of several
decimetre diameter following the steeply dipping bedding in the middle unit.
It has been suggested that the karst in the middle unit, is a mature system (JV.
Stucky/Electrowatt., 1992, Koleini et al., 2012), generated during a period of strong
hydrothermal activity (hypogenic karst), because signs of highly mineralized former ground
water circulation are common. This hypothesis may be supported by the presence of hot
springs and suggests that the karst should also have developed in depth. The field
observations show about 24 springs present at the dam site of which 11 springs are hot water
springs with temperatures of 30º- 40º.
In general, it is possible to zone the units into three principal zones correlating with the
stratigraphy. The upper zone of the Asmari Formation comprises a very heterogeneous
alternation of thinly bedded limestones with marls and siltstones resulting in a fairly
impervious rock mass of moderate to weak rocks.
The central zone is more homogeneous and thickly bedded. Characteristic lithology are the
vuggy, porous limestone. The rock strength is generally intermediate to high and karst
features are well developed (Figure 4.6.6).
Finally, the lower zone of the Asmari Formation is characterized by a very regularly bedded,
fine grained brown limestone at the top, very thickly bedded cherty limestone in the centre
and an extremely regularly alternation of thinly bedded limestone with thin marly beds at the
base. The strength is moderate to high and the permeability is low, but locally strong
karstified layers have been observed.
4.6.3.2. Speleological Reconnaissance
The exact identification of the three dimensional cavern developments is key to the final
decision on how to plug or to circumvent the karst systems in the most economical and most
efficient way, and how to incorporate the plugging of these structures into the grout curtain.
For this reason, all detected caverns have to be speleologically investigated as well as
geologically surveyed.
During the excavation of adits and grout galleries, seven large caverns were discovered.
The two largest are Golshani's Cave, GG 802 on the right flank and Saidi Cave, GG 835 in
the left flank (Figures 4.6.7, 4.6.8 and 4.6.9). Golshani's cave (150 000 m3, Fazeli, 2007) was
investigated from elevation 802 m down to elevation 740 m. The bedding planes and joint set
Js1 are the main discontinuities in this cave. It is obvious that several channels that belong to
this cavern extended above 802 m and others below 740 m. The vertical dimension of the
cavern is more than 70 m and horizontally more than 40 m. The origin of Saidi Cave was
caused by different discontinuities, although joint system Js.1 played a primary role.
445
0
1.0
2.0m
Figure 4.6.7. Several channels related to cavern development in the right flank. The
bedding planes and Js.1 are mainly responsible for cave development.
4.6.3.3. Permeability at the Dam site
Permeability values between 1.2 X 10 -4 - 1.2 X 10 -6 cm/s, represents very low fractured
and very low permeable rocks, from 1.2 X 10 -3 - 1.2 X 10 -4 indicate low fractured and low
permeable rocks, and permeabilities from 1.2 X 10 -2 - 1.2 X 10 -3 cm/s, indicate permeable but
low karstified rocks. Only the range from 1.2 X10 -1 - 1.2 X 10-2 cm/s, indicate karstified or
strongly karstified rocks. The permeability of intensively karstified and fractured rocks is
usually more than 1.2 Χ 10 -1 cm/s (MG.co, 1993).
Consequently, from a leakage point of view, it is obvious that a rock mass with a
permeability of more than 1.2 Χ 10 -3 cm/s plays a key role, but permeability of more than 1.2
-2
Χ 10 cm/s has a decisive influence on the successful design of the anti seepage treatment.
Based on the borehole logs and Lugeon tests only, the rock mass at the dam site appears
not to be highly karstified. Some Lugeon tests do indicate the presence of karstification, but
during the drilling program, no karst voids were encountered. This fact was surprising. There
is a pronounced anisotropy in the permeability due to steep and subvertical discontinuities,
which display different Lugeon values for vertical and inclined boreholes.
The hydrogeological features at the dam site are the consequence of the regional geological
setting. The impervious and compressed anticline core seems to be a barrier for underground
water filtration from the upper erosion base levels to the lower steps. A number of springs
(phreatic water as well as thermal water) discharge along the gorge section upstream of the
barrier.
Apparently, there is no hydrogeological possibility for the underground water to penetrate
downstream. Water movment towards the regional base level (Ghir Plain) has been
interrupted by a deep long and wide hydrogeological barrier consisting of the Pabdeh and
partially of the Lower Asmari Formations.
Under these circumstances, the bottom of the gorge is a local, but the only active erosion base
for all upstream waters. The rapid post- Pliocene uplift (one mm/year) caused a rapid fluvial
446
process where the bottom of the Karzin gorge is cut by rapid fast fluvial erosion
perpendicular to the anticline axis.
Well developed subvertical fracture systems, together with frequent and steep joint systems
along with the bedding planes created a fully connected network for preferential filtration of
water. i.e. the limestone rock mass is fully exposed to karstification processes. The karst
aquifer is in constant adjustment to the level of the gorge bottom. As the discharge zone
became progressively lowered, the hydraulic gradients towards the gorge bottom increased.
Consequently, turbulent underground flows eroded the walls of initial karst conduits
producing the large channels and caverns.
The karst features could only develop up to the gorge (limestone bedrock), i.e.,
approximately to elevation 740 - 735 m. This is the real base of the karstification in the gorge
area. Therefore, it has to be assumed that down to elevation 735 m karst conduits exist.
Theoretically, a siphonal circulation of phreatic water could provoke karstification deeper
than the erosion base level, but in the Karzin gorge there is apparently no evidence for such a
process. Deeper karstification can also be the consequence of upward hot water flows.
As referred to before, the limestone ridges on either side of the dam site are subparallel
systems of vertical and subvertical discontinuities (shears, faults), running across the axis of
the Changal Anticline. Karstic features developed along these discontinuities and along the
steeply dipping bedding planes. They can possibly provide a direct hydraulic connection
between the reservoir and the gorge downstream of the dam, i.e., there is the possibility of
substantial seepage from the reservoir bypassing the dam. Thus, the grout curtain has to be
placed in such a way to intersect these discontinuities.
Generally, the hydrogeological anisotropy is one of the important characteristics of the
dam site. Karst porosity dominates in the upper part of the Middle Asmari limestone unit as
referred to before. A number of karst channels have been discovered in the rock mass from
reservoir elevation (855 m), down to this level. Most frequently, karst chimneys with
apertures from a few centimetres to a few metres have been detected. In addition, large caves
with volumes of thousands of cubic metres have been discovered on both valley sides. The
volume of the largest one found on the right flank (Golshani Cave) is 150 000 m3 (Figure
4.6.8 and 4.6.9). These large caves are partially filled with huge limestone blocks with some
blocks more than 10 m3 in size.
The exact depth of the Karstic features is uncertain but the speleological investigations are
not finalized yet. According to the thermal field, measured in only one deep hole drilled from
river level, permeability due to karstification is indicated only at elevation 690 m- 710 m. In
the same hole the permeability tests show more than 100 Lu at elevation 725 m. Some
negligible peaks at elevations 620 m and 590 m of less than 10 Lu are too small to be
interpreted as due to karstification.
The geophysical logs did not detect any particularly problematic geological conditions along
the boreholes and wells.
In general the Lugeon tests on the dam axis indicate the permeability of the Asmari
Formation as follows:
a) Upper Asmari, fairly impervious
b) Middle Asmari, very low to very high in the upper part
c) Lower Asmari, generally low but locally very high
447
Left Bank
Right Bank
Faults
F1
F2
853
853
835
835
802
802
775
740
738
Diversion Tunnel
0
Limit of Grout Curtain
20
40
60
80
100 m
GROUT CURTAIN LONGITUDINAL SECTION
AND APROXIMATE POSITION OF CAVITIES
Figure 4.6.8. Schematic presentation of the longitudinal section of the grout curtain and approximate
positions of cavities at the Salman Farsi dam (after Stucky-Electrowatt, 2001).
G1
Upstream
0+482
P1
0+422
GG 769R
0+467
P
G
Downstream
0+373
0
G
P
G1
830
830
820
820
810
810
800
800
790
790
780
780
770
770
760
760
750
750
P1
10
20
30
40
50 m
0+345
GG
GG
76
9R
80
2R
Figure 4.6.9. The geological map and section of Golshani Cave in the right flank of the Salman Farsi dam
(after Stucky-Electrowatt, 2001).
4.6.3.4. Reservoir Watertightness
The Salman Farsi reservoir is located in a valley composed of the following generally
impermeable formations.
 Razak; red shale, siltstone, marls and gypsum
 Mishan; grey marl and shelly limestone
 Bakhtiary; unconformable deposited massive conglomerate and sandstone.
448
The reservoir will partially be in contact with the almost impermeable Upper Asmari
formation. The youngest sediments in the reservoir are widespread alluvial gravel and
terraces (Figure 4.6.10).
Only in a few localities, close to the dam site, will the reservoir water come into direct
contact with karstified limestone. In addition, the Yarg Spring area is a questionable location
for seepage. In the reservoir area, no drilling investigations have been executed, except for
three boreholes in the vicinity of the Yarg Spring.
Figure 4.6.10. The southern part of the reservoir area of the Salman Farsi dam project on the northern
limb of the Changal Anticline. The bedrock consists of almost impermeable rock successions of the
Fars Group. The Karbasi Anticline, which forms the northeastern boundary of the reservoir can be
seen as well (2007).
4.6.4. Tectonic Setting
4.6.4.1. Regional Tectonic
The Salman Farsi dam site and reservoir are situated in the Zagros Mountains tectonic
province of southwestern Iran (Figure 4.6.11). The dam is situated on the northern flank of
the Changal Anticline (Figure 4.6.10) in the Karzin Gorge which follows the Zagros trend.
With regards to the reservoir, the relevant anticlines are Changal, Palang and Karbasi. The
axes of these anticlines are parallel to each other. The Karbasi Anticline represents the
northern rim and Changal represent the southern rim of the future reservoir.
These folded structures are situated between the reservoir area and the lower erosion base
level (Ghir Plain). It is an asymmetrically folded structure, striking generally WNW-ESE and
plunges steeply northwards. The fold axis is oriented 295°/15°. Related to this fold is a
parasitic anticline that is very important for the water tightness of the reservoir on the
northwestern part of the dam site (fold axis 285°/05°). The Changal Anticline is separated
from the Palang Anticline by a very tight northwest plunging syncline.
449
The dip of the Asmari Limestone layers at the site area is 50°-60° NNE. The very steep,
NE dipping and reverse Dareh Siah Fault cuts the core of the Changal Anticline downstream
from the dam site. Genetically, this fault belongs to the folding phase. The Asmari Formation
has been thrusted on to the Razak Formation in the northwestern part of the site due to the
Dareh Siah Fault activity (Figures 4.6.12 and 4.6.13).
0
50
100
150
Km
Figure 4.6.11. The major seismically active faults in the study area. The map shows the distribution
of active faults and demonstrates the relationship between the slip vectors and compressive axis,
obtained from the solution of the focal mechanism of earthquakes, and GPS velocities (International
Institute of Earthquake Engineering and Seismology- Iran, 2003).
Due to the presence of the Precambrian Hormus Salt Formation, deduced from the
frequent salt domes, the sedimentary pile has been detached from the basement explaining the
N-S to NNE-SSW oriented tectonic transport direction and the well exposed sequence of
gentle long whale back anticlines separated by strongly folded and sometimes very tight
synclines.
The deformation started in the Pliocene as signaled by the unconformable deposition of the
fluvial, deltaic Bakhtiary conglomerates on the Agha Jari and Mishan formations, as the
erosion products of rising anticlinal hills. The folding continued through the Pleistocene
tilting the Bakhtiary beds within the synclines. At the same time high angle thrust faults
developed.
At a later tectonic stage, important right-handed strike slip faults developed, cutting and
displacing the anticlines by several kilometres. The most important of these structures are
from west to east the Karbasi, Sarvestan, Lar and the Bakhtegan Faults. Like in the case of
the Karbasi Fault, salt domes are associated with the strike slip portion of these structures,
which extend through the entire sedimentary cover, perhaps reaching the basement. These
faults accommodated the oblique deformation within the fold belt caused by thrust and slip
movements along the Kazerun and Main Zagros faults (Figure 4.6.11).
The present tectonic phase is expressed by strong seismicity. Fault plane solutions and the
focal depth of the recent earthquakes indicate that the seismicity is related to northwest
421
southeast striking high angle reverse faults (dipping NE or SW) of 8 to 20 km depth in the
uppermost basement.
The fact that several ductile salt layers are distributed within the sedimentary cover
absorbing the deformation, explains the absence of directly related surface faults (ZagrosType Earthquakes along buried faults). One of these buried seismic trends, based on
historical destructive earthquakes in the Ghir area is located about 15 km south-southwest of
the dam site. Reactivation of earlier surface discontinuities and sympathetic faulting have
also been observed.
Dareh Siah F
Figure 4.6.12. The Salman Farsi dam site is situated on the northern flank of the Changal Anticline
which follows the Zagros trend. The Karbasi Anticline represents the northern rim and the Changal
Anticline represents the southern rim of the future reservoir (2007).
4.6.4.2. Large Scale Structures in the Project Area
a) A small salt dome and a system of left-handed strike slip faults cutting the Kaftar
Anticline. The importance of this structure for the seismic hazard has to be verified in
the field.
b) The Karbasi Anticline (Asmari-Jahrum Formation) which borders the northern part of
the future reservoir.
c) A large syncline in the reservoir area created by disharmonic, strongly folded Pliocene
to Pleistocene rocks (Razak, Mishan, and Bakhtiary formations) and Quaternary
cemented mainly gravely alluvium. The syncline is bordered to the northwest by the
two arms of the southeast plunging limestones of the Naura Anticline. The Ghareh
Agahaj River flows in the axial depression of the syncline.
d) The Changal Anticline which rims the reservoir to the south. Related to this fold is a
parasitic fold which is very important for the water tightness of the reservoir and which
has been mapped northwest of the dam site.
e) The Dareh Siah Fault cutting the core of the Changal Anticline (Figures 4.6.12 and
4.6.13).
f) A very tight northwest plunging syncline separating the Changal Anticline from the
Palang Anticline.
424
g) The South Dashte Ghir Fault to the south of the large Ghir plain. The seismotectonic
importance of this high angle reverse fault has already been discussed.
Dareh Siah F.
Figure 4.6.13. The Dareh Siah Thrust Fault cuts the core of the Changal Anticline then continues to the
northwest of the dam site and caused the Asmari Formation thrusted on to the Razak evaporites
Formation.
4.6.4.3. Joint Study and Direction of Principal Stresses at the Salman Farsi Dam site
Apart from the bedding planes of sedimentary origin, six different kinds of discontinuities
(small-scale faults and joints) which reduce the quality of the rock mass and decrease the
slope stability rate can be identified at the dam site.
The stereographic projections of discontinuities including a Contour plot, Rosette plot and
Pole plot (Dips©) are shown in Figure 4.6.14. The principal sets of discontinuities are Js.1,
Js.2, Js.3 and Bp. (bedding plane). Two less important of the discontinuity sets that are
accessory joint sets are Js.4 and Js.5.
Bedding planes are the most evident feature forming structures spaced 0.4 to 1.2 m in the
limestone, 0.1 to 0.6 m in the marly limestone and less than 5 cm in the marlstone, and also
represent the preferred detachment surface according to the mechanical competence contrast
of the rock wall.
Small-scale faults of maximum 10 m length and 2 m displacement can be observed in the
upper unit of the Asmari Formation. The discontinuity apertures are from mm to cm and
filled by small fault breccia not washed out by erosion. In the central and lower units, the
faults are mostly left-handed, less frequent but longer. On the right bank a very clearly visible
structure can be observed about 100 m west of the dam, displacing the beds of the middle unit
about 1m. The fault surface is rough, the opening very small and the wall rock fractured. This
structure is more than 100 m long and may extend the same distance downwards, but is
covered by colluvial deposits.
On the left flank, a fault has been followed from the outlet of the diversion tunnel up to the
ridge. The displacement varies from few centimetres to 1.5 m. The aperture is few
centimetres, washed out in the upper parts and filled by fault breccia at lower levels where a
422
hot water spring occurs. The general orientations of the faults coincide with joint systems Js.1
and Js.2. The stereographic projections of faults are indicated in Figure 4.6.15.
Joint system Js.1, Js.2 and Js.3 dips very steep. These discontinuities often rough surfaces
are closed without filling with spacing between 0.5 and 3 m. Joints on the left flank are
uniformly oriented and generally belong to system Js.2 but on the right flank the distribution
is more scattered. The distribution of discontinuities according to the rock units and abutment
side is shown in Figure 4.6.14. Flat lying joints have been exclusively measured in the upper
units of the right flank.
The bedding planes on the left abutment are very uniformly orientated and are mainly of
system Js.2. The joint distribution on the right abutment shows Js.1 and Js.2 almost present in
equal density.
423
A
B
C
Figure 4.6.14. Stereographic projection of joints (discontinuity distribution) of the Salman Farsi dam
foundation rocks. A- Contour plot, B- Rosette plot, and C- Scatter plot of joints (Dips©, equal area
projection-Schmidt net, lower hemisphere).
421
A
B
C
Figure 4.6.15. Stereographic projection of faults (general orientation of small- scale faults) at the two
abutments of the dam site A- Contour plot, B- Rosette plot, and C- Scatter plot of faults (Dips©,
equal area projection-Schmidt net, lower hemisphere).
425
The bedding planes have a more scattered distribution. Figure 4.6.16 represents the
calculated main great circle orientations of the major joint systems and bedding planes and
their intersections on both sides of the dam foundation. The other joint systems Js.4 and Js.5
are poorly developed and their occurrence is very local, but because of their steep dip can be
considered to decrease the stability.
The major joint sets based on the stereographic projections are as follows:






Js.1: 131°/ 81°
Js.2: 115°/ 85°
Js.3: 280°/ 77°
Js.4: 294°/ 89°
Js.5: 149°/ 63°
(B.p) bedding planes: 019°/ 55°
The direction of the major principal stresses based on the discontinuity systems especially the
bedding planes dip/direction in 2D view, are as follows:
1: 205°/ 0.0° (max. principal stress)
2: 295°/ 0.0° (intermediate principal stress)
3: 0.0°/ 90° (min. principal stress)
Shortening Direction
Figure 4.6.16. The direction of 1 / Shortening at Salman Farsi dam site.
4.7. Petrographical Analysis of the Asmari Formation at five Dam Sites
The petrographic examinations of about 250 thin sections are presented in detail in
Appendix 1 to 5. The classification proposed by Dunham (1962) and Folk (1962) have
proved to be the most practical. Modifications suggested by Embry and Klovan (1971),
Wright (1992) and Strohmenger and Wirsing (1991) are also useful.
The most widely used classifications are those of Dunham (1962) and Folk (1962). Dunham
(1962) classification can equally well be applied in the field, in investigations of cores, and in
laboratories.
The porosity types are defined based on Choquette and Pray (1970) which represents the
percentage of the bulk volume of a rock that is occupied by interstices, whether isolated or
connected. This definition describes the total porosity which must be separated from the
426
effective porosity. The later is the percentage of the total rock volume that consists of
interconnected pores.
The petrographical analyses according to the above methods are summarized in Table
4.7.1. In general, the Asmari carbonate rocks in the study area are classified into
Intrabiomicrite to Biodolomicrite, Wackestone to Packstone, except at Salman Farsi that
indicates locally Biointrasparite and Grainstone. Dolomitization is locally well developed in
the middle parts of the Asmari Formation at Salman Farsi and Seymareh dam projects.
The bioclast elements (biota) consist of Foraminifera, Bivalve (mainly Rudists), Echinoid
shells, Serpolide shell, Calcisponges, Bryozoan fragments and calcareous Red Algae. The
identifiable Foraminifers that constitute the main bioclasts elements are generally as follow:
Peneroplis sp., Archaias sp., Borelis sp., Ditrupa sp., Rotalia sp., Operculina sp.,
Nummulites sp., Meandropsina sp., Heterostegina sp., Miogipsina sp., Elphidium sp.,
Asterigerina sp., Dendritina sp., Lepidocyclina sp., Haplophragmium sp., Austrotrillina sp.,
Miliolides such as Biloculina, Triloculina, Quinqueloculina, and Planktonic Foraminifera
such as Globigerina sp. and Globorotalia sp.,
The basic porosity types were defined by the Choquette and Pray (1970) chart which classify
porosity into three main types, particularly; fabric-selective, non fabric-selective and fabricselective or not.
The minimum and maximum porosity are estimated between 0.3% to 15.7% which relate
to the Middle Asmari at Salman Farsi and the Lower Asmari at the Karun-3 projects
respectively. However, an abnormal porosity value (19.4%) was related to the upper most
part of the Upper Asmari at Salman Farsi, due to the Darreh Siah fault zone.
The percentage of total porosity has been measured by microscopic quantitative
method/point-counting (Punktfeld-Method after Sander 1951). This method was developed
by Glagolew (1933) and improved by Chayes (1956). The results of porosity values are
presented in Table 4.7.1 and Figure 4.7.1.
P
o
r
o
s
i
t
y
%
Min
Max
Upper Asmar (U)
Middle Asmari (M)
Lower Asmari (L)
Figure 4.7.1. The minimum/maximum porosity values based on petrographical analysis of rock foundations
at Karun-3 (K-3), Karun-4 (K-4), Seymareh (Se), Marun (M) and Salman Farsi (Sa) dam projects. L
(lower), M (middle), U (upper).
427
Table 4.7.1. Summary of the petrographical analysis of five dam foundation rocks.
Dam site
Unit
Porosity%
Porosity type
U.Asmari
Marly limestone and marlstone, Biointramicrite, wackestone,
porosities locally filled by microsparry calcite,
0.75-13.8
L.Asmari
Limestone, marly limestone, locally dolomitic limestone,
Intrabiomicrite, wackestone to packstone, porosities partly filled
by sparry calcite cement, Dolomitization locally developed
1- 15.7
Vuggy: 46%
Fracture/channel: 34%
Others: 20%
Karun-3
U.Asmari
Karun-4
Seymareh
Marun
Salman Farsi
Petrography
Limestone, marlylimestone, marlstone Intrabiomicrite, mudstone
to wackestone, porosities are filled partly by sparry calcite.
Karst features
Vuggy zones
Solution cavities
Vuggy zones
Solution cavities
1-2 m
Non to slightly
karstified
0.5- 5
M.Asmari
Limestone, dolomitic limestone, marlstone Intrabiomicrite,
dolomicrosparite, wackestone, dolomitization locally well
developed, porosities partly filled by sparry calcite
1- 7
L.Asmari
Limestone, marlylimestone, calcareous marls Intrabiomicrite,
wackestone to packstone, porosities are filled partly by sparry
calcite cement.
0.75- 15.2
Highly karstified
U.Asmari
Crystalline bioclastic limestone, marlylimestone Intrabiomicrite,
wackestone to packstone Porosities are filled partly by sparry
calcite cement
0.75- 4.4
Karstified,
dissolution cavities
M.Asmari
Crystalline limestone, dolomitic limestone, marlylimestone
Biodolointramicrite, wackestone to packstone, dolomitization
widespread, karstification well developed, cavities partly filled by
calcite cement.
0.6- 7.5
L.Asmari
Microcrystalline limestone, marlylimestone Intrabiomicrite,
wackestone to packstone, cavities are filled by coarse
blocky/granular calcite cement.
1.4- 5.2
Karstified
U.Asmari
Limestone, marlstone interbeds Intrabiomicrite, wackestone,
cavities are partly filled by coarse sparry calcite cement.
2.1- 5.4
Highly karstic
M.Asmari
Crystalline limestone, marlylimestone, marlstone interbeds
Biopelmicrite, wackestone to biolitic boundstone, Locally
recrystalization of micrite to microsparry calcite cement
1.4- 11
L.Asmari
Microcrystalline limestone, marlylimestone Intrabiomicrite,
wackestone to packstone, cavities are filed partly by coarse sparry
calcite cement.
1.3- 14.9
Karstified
U.Asmari
Alternation of limestone, dolomitic limestone, marlylimestone,
marlstone, porosities partly filled by microsparry calcite cement
Biointrasparite, grainstone, locally dolomitization
1.5- 19.4
Karstified
dissolution cavities
M.Asmari
L.Asmari
Crystalline limestone, dolomitic limestone, marly limestone
Biodolomicrite, wackestone to Intrabiosparite, grainstone
Extensively Dolomitization.
Alternation of fine grained limestone and marlstone Biomicrite,
packstone to boundstone, Porosities partly filled by microsparry
calcite cement.
428
0.3- 8
1- 5.6
Vuggy: 42%
Fracture/channel: 36%
Others: 22%
Vuggy: 74%
Fracture/channel: 17%
Others: 9%
Vuggy: 64%
Fracture/channel: 11%
Others: 25
Vuggy: 68%
Fracture/channel: 11%
Others: 21%
Slightly karstified
Karstified
Caves 100s m3
Karstified
Chimney and caves
100s m3
Isolated cavities
The porosity type results are plotted on a ternary diagram of pore types (Figure 4.7.2). The
ternary porosity type plot provides information on the shapes and origin of pore systems. Two
distinctive areas; namely groups 1 and 2 are indicated and related to Karun-3, Karun-4 and
Seymareh, Marun, Salman Farsi cases respectively.
Vug
Se
Sa
M
Se: Seymareh
Sa: Salman Farsi
M: Marun
2
K3
K4
1
K-3: Karun-3
K-4: Karun-4
Oth
Fr, Ch
Figure 4.7.2. Ternary porosity type plot (ternary diagrams of carbonate pore types) provides
information on the shapes and origin of pore systems. The plots are based on quantitative data
derived from point counting of thin sections.
The percentage of Fracture/Channel porosity type for groups 1 and 2 are about 35% and
13% respectively. This can be explained by a higher fracture density due to more tilting or
curvature of strata (70°- 90°) at the south-western flanks of anticlines resulting from tectonic
movements. In general the porosity values based on the Cherenyshev and Dearman (1991)
classification indicate Medium to Extremely high porosity for the Asmari limestones.
4.7.1. Standard Facies Zones and the Wilson Model
The succession of major facies belts on rimmed tropical carbonate platforms was used by
Wilson (1975) to establish a Standard Facies Model depicted as a basin-to-shore transect and
comprising Standard Facies Zones. The basis of the model is the recognition of consistently
recurrent patterns of carbonate facies in the Phanerozoic records and the environmental
interpretation of these patterns by using characteristics of Holocene sedimentation patterns
(Flugel, 2004).
In this regard the analysis of samples resulted from petrographical studies (allochemical,
orthochemical elements) generally indicate that the Asmari succession carbonates are mainly
related to Facies Zones (FZ) 6, 7, and 8 of Wilson which refer to;
429
 6- Platform-edge and platform sand shoals
 7- Open-marine Platform
 8- Restricted-marine platform
In addition at the Karun-3, Karun-4 sites the upper Asmari samples indicate planktonic
foraminifera’s assemblages which correspounds to Zone 1 of Wilson Facies, namely;
 1- Basin and deep shelf- Deep sea
4.8. Hydrogeology
4.8.1. Weathering and Karst Features
Rock weathering is generally a near-surface feature but localized weathering was found at
depth in some localities in dam abutments and beneath the riverbeds. Slight penetrative
weathering into the rocks along discontinuities was observed in some drill core with iron
oxide such as hematite, limonite staining and clay mineral fillings due to weathering
widespread on discontinuities. The karstification of the Asmari limestone is the main
characteristic of this formation. The dissolution of limestone involves three principal
components: carbon dioxide, water, and calcium carbonate. Initially, atmospheric carbon
dioxide diffuses into the moisture within the air or soil and simultaneously becomes hydrated
to form carbonic acid (Blair, 2009):
CO2 + H2 O
H2 CO3
In contact with limestone, carbonic acid dissolves the calcite. The reaction is often presented
as:
-
Ca2++ 2HCO3
dissolved limestone
CaCO3 + H2 O
limestone
The time required for aggressive water in karst regions to be neutralized or to reach
saturation equilibrium varies considerably, depending on a number of factors such as
temperature, turbulence, variations in the partial pressure of carbon dioxide, dilution,
presence of other acids, and surface area of limestone (Blair, 2009). To achieve equilibrium
may require several days. However, laboratory studies suggest that most of the limestone
dissolution resulting from an influx of fresh aggressive water may occur within minutes to a
few hours (Sweeting, 1950; Jakucs, 1977; Ritter, 1978). Additional acids, such as organic
acids from soils and most recently sulphuric and nitric acids from acid rain, will contribute to
the dissolution of carbonate rocks.
Three factors drive the development of karst; the lithology, distribution of rock type and
the occurrence of discontinuities. In addition to the composition of limestone, the thickness of
individual beds, the nature of interbeds, especially shaly beds, and lateral facies variations
affect the style and degree of karstification (Dreybrodt et al., 2002; Blair, 2009). The main
factors that influence rock permeability are the occurrence of fractures and fissures in the
rock mass. From the lithological point of view, we have to distinguish the general tendency to
strong dissolution of the porous, vuggy, micritic limestone from the more resistant, less
porous, recrystalized, finely to medium-grained calcarenite, whereas marls and marly
limestones are almost impervious (Blair, 2009).
431
Dolomitic limestones (or dolomites) are rocks which have undergone chemical changes
resulting in the replacement of some of the calcium by magnesium. Magnesium carbonate
(dolomite) has a different crystal structure to calcium carbonate and this creates additional
void space in the rock which can increase the development of permeability and in some cases,
karstification. The nature of the limestone strongly influences its susceptibility to
karstification.
Pure limestones are more susceptible for dissolution than impure limestones. Another
strong influence is the geological structure: folding of the limestone causes fracturing and the
formation of a network of fissures along which water can penetrate and begin to dissolve the
rock. In general, pure limestones tend to be brittle, allowing extensive open fractures, while
impure limestones tend to deform more readily, sealing up the fractures and impeding water
movement. The degree of karstification is significantly reduced where there are inter-bedded
shale layers which restrict water movement and where very strong deformation causes resealing of fractures with crystalline calcite (Blair, 2009).
The observations indicate that the Asmari limestone cavities can be divided into two main
groups;
 Cavities resulted by simultaneous diagenetic process
 Cavities resulted by karstification process
The first group is mainly circular to elliptical with maximum 20 cm in diameter, generally
constituting 5% of the rock mass volume. These features apparently do not show any
hydrogeological connection to each other.
The cavities resulted from karstification processes are partly filled by clay and silty materials
with dimensions commonly about 1 to 2 m. The huge caves, caverns and chimnies tens of
metres in dimension are recognized especially in the northern flank sites where the Seymareh,
Marun, and Salman Farsi Dams are situated (Figure 4.8.1).
In general, highly karstic features due to solubility of the rock mass are observed in the
Asmari Formation limestone. The karstifications are mainly well developed along
discontinuity surfaces essentially on bedding planes. The fracture and joint systems constitute
well developed patterns of water pathways in rock mass, and control infiltration of water in
depth.
SW
NE
Asmari F.
Karun-3
Karun-4
Seymareh
Marun
Salman
G.F.
Gachsaran F.
Pabdeh F.
Figure 4.8.1. Block diagram showing three successive formations (Pabdeh, Asmari and Gachsaran) at the
Zagros folded belt and relative dam site localities at the two flanks of anticlines.
434
The caves, stalagmites, stalactites, karstic channels (30-100 cm in diametre) and enlarged
fissures resulting from water dissolution are common. The caves have almost longitudinal
shapes parallel to the bedding planes and at the intersection of main discontinuities
karstification is well developed. The sections of caves are circular to elliptical.
Field observations indicate many springs exist at the dam localities (12°- 25°) with some of
them, especially at Salman Farsi, hot water springs with 35°- 42° C temperatures. This can
explain the high solubility potential of the Asmari limestone due to active mineral water
derived from depth (hydrothermal solutions).
Except for the lower part of the Asmari at Karun-4 with high karstification, the karst features
at Karun-3 and Karun-4 dam localities are limited to slight to moderate karstification,
solution cavities and vuggy zones, with maximum dimensions about 1 to 2 m. But the field
observations in the reservoir areas indicated large to huge caves (50x30x20 m) in the Asmari
succession.
Field investigations at the northern dam sites (Seymareh, Marun, Salman Farsi) also
indicate various geological and karstification conditions. Karst development is common in
this case with frequent, karst chimneys with apertures from a few centimetres to a few
metres. In addition, large caves with a volume of thousands of cubic metres have been
discovered on both sides and under river beds at dam localities. The volume of the largest one
found on the right flank of the Salman Farsi project (Golshani Cave) is 150 000 m3. At the
Seymareh and Marun projects some large caves have also been detected in both flanks and
under the river bed in the downstream area.
Immediately after the excavation of tunnels in the Asmari limestone the surface springs dried
up and hot water was discharging into the tunnels. A smell of H2 S emanated from these
waters.
Sulphide rich water (1-15 lit/min) and slightly bitter and brackish water mainly originate
from the Gachsaran/Razak Formation and occur downstream from the Asmari limestones.
The chemical compositions of spring water are calcium sulphate and sodium chloride and
carbonate (MG. co., 1984, 2003). Springs with this composition indicate, hydraulic
connections between the two Asmari and Gachsaran Formations as well.
SW
NE
Asmari Formation
Gachsaran Formation
Pabdeh Formation
Figure 4.8.2. The karstification model at the northern flank of anticlines in the Zagros folded belt
and the role of the Gachsaran/ Razak Formation evaporites on karstification of the Asmari
limestone.
432
Closed depression caves, sinkholes and collapse sinks are well developed in the Gachsaran
Formation due to chemical and physical dissolution of the evaporite rocks (Figure 4.8.2). The
Asmari Formation limestones are influenced by active mineral solutions resulting from the
Gachsaran Formation and this is the main factor for the extensive development of karst
features in the Asmari limestones, especially in the upper and middle units. These units of the
Asmari Formation are the main foundation rocks at the Seymareh, Marun and Salman Farsi
dam sites. The dissolution mechanism of Gachsaran/Razak evaporaties due to meteoric and
underground waters in addition to the four stages of development of karst features in the
Asmari limestones can be explained based on Figure 4.8.3. When gypsum is dissolved by
underground water activities, the surrounding rocks collapse and then open space is then
filled by collapsed rocks and create a funnel with karst breccia at the bottom of hole.
The Gachsaran/Razak Formations consist of hundreds of metres of alternating layers of
gypsum, anhydrite, salt and coloured marls with high flexibility and solubility and have been
extensively karstified to zones with various dimensions. These formations are widely
distributed in the Zagros region and contain evidence of karst in most areas (Figures 4.8.3,
4.8.4 and 4.8.9).
The disruption of the Gachsaran/Razak evaporite sequence caused by tectonic movements
is the main factor causing the infiltration of active mineral waters to develop karstification in
depths. This phenomenon can be observed not only at the surface but also at depth (data from
exploratory drillings). In some localities, due to impervious layers of marls, a perched water
(perched aquifer) level can occur in the Gachsaran Formation (Figure 4.8.2). The dimensions
of these sinkholes vary between 2 m to 15 m, based on field observations. One of the biggest
sinkholes, with diameter 70 m and 10 m depth has been detected in the Seymareh dam site
reservoir (Zam Zam Hole).
A
C
Collapse
B
D
Figure 4.8.3. Schematic geological section through the Asmari-Gachsaran/Razak contact and evolution
of karstic collapse feature. The dissolution of the Gachsaran/Razak evaporites (gypsum, anhydrite, salt,
marl) due to high solubility of evaporites sequence (solution-collapse structures). The water bearing acid
(H2SO4 solutions) will be the outcome of the process, which can dissolve the Asmari Formation
limestone and accelerate the karstification process.
433
Gypsum is one of the most soluble of the common rock minerals; and it is readily
dissolved to form caves, sinkholes, collapse columns, swallow holes, and other karst features
that are typically found in limestones and dolomites. The principal difference is that gypsumkarst features can form rapidly in a matter of weeks or years, whereas carbonate-karst
features typically take years, decades, or centuries to form. The four basic requirements for
gypsum karst to develop are (Johnson, 1996a):
 A deposit of gypsum;
 Water unsaturated with CaSO4
 An outlet for escape of dissolving water and
 Energy to cause water to flow through the system
When all four of these are met, dissolution of gypsum can be rapid in terms of geologic time
(Johnson, 1996).
The solubility of CaSO4.2H2O ranges from about 2 200- 2 600 ppm in the temperature range
of 0°- 10° C (Hardie, 1967; Blount and Dickson, 1973).
Evidence of gypsum karst includes surface and shallow-subsurface features, such as caves,
sinkholes (dolines), karren, disappearing streams, shallow holes, springs, collapse structures,
and result in the dropping of drill bits and /or loss of drilling fluids while drilling through
gypsum beds.
All these karst features and many more, are identical in character and genesis to those
found in carbonate rocks. In fact palaeokarst, brecciated zones, and other karst features found
in some carbonates may have been initiated by earlier dissolution and karst development in
gypsum that is interbedded with the carbonates (Sando, 1988; Friedman, 1997; and Palmer,
2000).
A
B
Figure 4.8.4. Closed depression in red marls bearing gypsum of Gachsaran Formation (A). Karst
development in Razak evaporites formation at the Salman Farsi dam site. Dissolution is mostly pronounced
along joints and bedding planes (B).
Gypsum karst can be accelerated by human activities. Gypsum-karst problems are caused by
the same activities that cause problems in carbonate terranes such as;
 building structures that induce differential compaction of soils above an irregular
gypsum-bedrock surface;
 building structures directly upon gypsum collapse features; and
431
 impounding water above, or directing water into a gypsum unit where soil piping can
divert water (and soil) into underground gypsum cavities.
(Solution-collapse str.)
Asmari
Formation
(Solution- collapse str.)
A
Gachsaran Formation
Gachsaran Formation
B
Figure 4.8.5. Some solution- collapse structures in Gachsaran Formation due to high solubility and erodible
evaporite rocks. Gypsum-dissolution at the region generates sulphate-rich water then collapse of overlying
rocks into cavities occurs.
These human activities can cause land subsidence or can cause new or concealed
sinkholes and cave systems to open up; this can result in settling or catastrophic collapse of
the ground (Johnson, 1996b). In evaporite rocks, cavity formation, collapse, and ground
subsidence can developed within a few decades.
Some researchers reported that the dissolution of gypsum (CaSO4-2 (H2O) in the presence of
NaCl will be raised (e.g. Ford and Williams, 2007), so that a solution with 50 to 150 gr/l of
NaCl can increase the solubility of gypsum up to 6 to 7 times (Figure 4.8.7). Therefore the
high karstification of the Gachsaran Formation can be explained by this process.
In addition the Asmari succession limestones (CaCO3) can be influenced by acidic solutions
resulting from the deterioration of Gachsaran Formation evaporites as follows (Blair, 2009):
CaCO3 + H2 SO4
CaSO4 + 2H2O + CO2
This evidence clearly explains the well developed karst features in the Asmari limestones
in the northern flanks due to karstification processes in the Gachsaran Formation (Seymareh,
Marun and Salman Farsi dam sites). In addition, the considerable areas of the reservoirs are
also by the Asmari and Gachsaran Formations the two high karstified formations (Figure
4.8.6).
435
Residential
area
Mishan
Formation
Gachsaran
Formation
Reservoir area
Figure 4.8.6. The distribution of the Gachsaran evaporites rocks (mainly gypsum) at
reservoir area of the Marun dam site. The surface karstification and weathering features can
be observed as well. The residential structures are constructed almost on karstified rocks of
the Gachsaran Formation (2007).
CaSO4 (gr/l)
Caso4 (gr/l)
8
6
4
50
100
150
200
Nacl (gr/l)
NaCl (gr/l)
250
300
350
Figure 4.8.7. Illustrating common Ion, foreign Ion and Ionic strength effects.
Increase of gypsum solubility with addition of NaCl (after Ford and Williams,
2007).
436
Chapter 5
The Engineering Geological Characteristics of
the Asmari Formation Rock Mass
at the Construction Sites of Five
Large Dams
5.1. Introduction
In his chapter, the engineering geological characteristics of the Asmari Formation at the
five dam sites are discussed.
The engineering geological parameters of the rock mass in this research were determined by
using the results of rock mechanics laboratory tests in addition to Schmidt hammer field tests.
The petrographic characteristics have been determined from thin section studies from the
systematic sampling of outcrops and boreholes (Appendix 1 to 5). These samples were also
subjected to Schmidt Hammer (Haramy and DeMarco, 1985) field tests to provide UCS
values for index layers. Otherwise, the data are compared to mechanical laboratory test
results which have been obtained from Mahab Ghodss Consulting Engineering CompanyMinistry of Energy- Iran (MG co., 1984-2003).
All data, including rock quality designations (RQDs), core recovery, permeability and
point load test results are based on MG co. (1984- 2003) geological reports and field data.
The geotechnical information was collected during three periods, namely Feasibility Study,
Complementary Study, and the ongoing Final Design investigations. The geotechnical
investigation program was divided into two parts:
1) Laboratory tests; and
2) Site investigations consisting of the drilling investigation and test holes, excavation of
adits, tunnels and field mapping.
The laboratory test program included determination of uniaxial compressive strength
(UCS), triaxial strength, shear strength, poisson’s ratio, modulus of elasticity, specific weight
and suitability of the Asmari limestone for aggregate.
The rock mass classification and characteristics along tunnels and investigations of their
stability have been carried out with ordinary experimental data methods using RQD, RMR, Q
and GSI. The rock support and stand-up time of tunnels during excavation operations were
calculated in accordance with the RMR system (Bieniawski, 1989).
The Unwedge©-(Rocscience) geotechnical software was used to determine rock instabilities
in tunnels. The software is designed to be a quick, interactive and simple to use method to
analyse the geometry and the stability of underground wedges defined by intersecting
structural discontinuities in the rock mass surrounding an underground excavation
(Rocscience Inc. 2004).
In this research, RocLab©-Rocscience software has been used to determine rock mass
strength parameters (C- cohesion, Phi-friction angle, sigc- uniaxial rock mass compressive
strength, sigt- rock mass tensile strength and Em- rock mass modulus of deformation).
RocLab is designed to aid engineers, especially at the preliminary stages of design and
provides simple and intuitive implementation of the Generalized Hoek-Brown, BartonBandis, Power Curve and Mohr-Coulomb failure criteria. The program enables users to easily
visualize the effect of changes in input parameters on rock and soil failure envelopes such as
(Rocscience Inc. 2004):




sigci- unconfined compressive strength of intact rock,
GSI- Geological Strength Index
mi- Intact rock parameter (rock type)
D- Disturbance factor
437
5.2. Engineering Geological Characteristics of the Karun-3 Dam and Power plant
(Engineering Rock Mass Classification of the Asmari Formation)
5.2.1. Diversion Tunnel
5.2.1.1. Lower Unit- As.1 (Lower Asmari Formation- 4a1, 4a2, 4a3)
The diversion system consists of upstream roller compacted concrete and downstream
concrete cofferdams and 13 m final inside diameter (horse shoe) tunnel under the right flank.
Geological data for the tunnel are derived from surface mapping and five boreholes, BH106D, BH-107E, BH-110F, BH-114U and BH-115Z (Figure 5.2.1). The tunnel is constructed
in the Pabdeh Formation (3b) from 0.0 (intake) to 265 m and in the Asmari Formation (4a14a2) from 250 m – 450 m (outlet). The Asmari Formation along the diversion tunnel axis is a
fair to good quality limestone with RQDs generally ranging between 50% and 85%. The
tunnel passes through subunits 4a1, 4a2 and 4a3 of the lower Asmari Formation. The
permeabilities are fairly high and fall between 2x 10-4 to 1x 10-3 cm/s.
Legend:
Gachsaran F. (5a): evaprates
Geological Section along Diversion Tunnel- Karun 3.
Elevation (m)
BH-114U
U. Asmari (4b)
limestone and marl
L. Asmari (4a1, 4a2, 4a3, 4a4)
limestone, dolomite
750.0
BH-106D
Pabdeh (3b): marl
BH-115Z
700.0
BH-106D
BH-110F
650.0
3b
4a1
4a3
4a2
600.0
050.0
100.0
150.0
200.0
250.0
300.0
350.0
400.0
450.0
Figure 5.2.1. Geological section along the diversion tunnel at the Karun-3 Dam (after MG co., 1993).
Based on discontinuity surveys, which have been carried out along the tunnel route, the
following discontinuity sets are present (Table 5.2.1 and Figure 5.2.2).
Table 5.2.1. Discontinuity sets in the diversion tunnel.
Discontinuity Set
Bedding
Set A
Set B
Set C
Dip Direction (°)
47
135
180
149
438
Dip (°)
80 - 90
81
08
49
Figure 5.2.2. Contour plot and major plane plots of discontinuity sets in the diversion tunnel.
Spacing of the bedding discontinuities are extremely wide (7.6 m) and Joint set spacing is
wide to extremely wide (0.6 to 6 m).
In the Karun-3 Dam project 48 boreholes with a total length of 6 688 m and another 3 635
m for the final design were drilled. All of them have been logged by the Mahab Ghodss
Company and Acers International Ltd. staff. For each borehole the lithological and
discontinuity logs have been compiled. Core recovery (CR) and RQD were measured on a
run by run basis in every borehole. The mean weighted RQD were then calculated (Table
5.2.2).
Table 5.2.2. Rock Quality Designation (RQD) assessment of the Asmari Formation at the Karun-3 Dam.
Unit
As.2
ASMARI
FORMATION
As.1
Subunit
Lithology
Thickness
4b
Thin to thickly bedded marlstone and shale
200 m
4a4
Medium to thickly bedded marly limestone
and limestone
Thick to V.Thickly bedded limestone,
interbedded marly limestone
235 m
4a2
Very Thickly bedded limestone
63 m
4a1
Thickly bedded limestone, marly limestone
22 m
4a3
95 m
RQD
Poor- Good
(31%-83%)
Fair- Good
(51%- 82%)
Fair- Good
(74%- 81%)
Fair- Good
(70%- 85%)
Fair-Good
(50%- 84%)
The RMR value for the Asmari Formation (units 4a1, 4a2, and 4a3) in the diversion tunnel
based on Table 3.3. is assessed as follows:
Table 5.2.3. Assessment of Rock Mass Rating for the Asmari Formation (4a1, 4a2, 4a3).
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition discontinuities
Ground water
Adjustment for joint orientation
Value
116- 138
50%- 85%
0.6-2m, >2m
Slightly rough slightly weathered
Dripping to Wet
Fair
Total : 64-76 (Good)
439
Rating
12 - 12
13- 17
15- 20
25 - 25
4- 7
-5
From Table 3.4. the guidelines for excavation and support of a 15 m span rock tunnel for the
above RMR values are as follows:
Table 5.2.4. Rock support types for units 4a1, 4a2, and 4a3 in the diversion tunnel.
Rock mass
class
II – Good rock
Excavation
Full face, 1- 1.5m advance.
Complete support 20 m
from face
Rock bolts (20 mm diameter,
fully grouted)
Locally, bolts in crown 4.5 m
long, spaced 2.5 m with
occasional wire mesh
Shotcrete
25 mm in crown and in
sides if required
Steel sets
Non
The Stand up Time for the diversion tunnel is between 1×103 hours (41.6 days) and 1×104
hours (416.6 days) based on the Bieniawski (1989) stand up time graph for good quality rock
mass.
The Rock Tunneling Quality Index, Q based on six parameters RQD, Jn, Jr, Ja, Jw and SRF
(Table 3. 5) were calculated indirectly using equations 3.9 and 3.10 in section 3:
From these equations, the Q-values vary between 35.1 (Good Quality) and 268.6 (Extremely
Good Quality)
The geological strength index (GSI) based on two simple equations of 3.11and 3.12 which
were introduced by Hoek and Brown (1997) was calculated for the Lower Asmari Formation
as follows:
The GSI then falls between 59 and 71
The rock mass strength with input data, UCS, GSI, mi and D (disturbance factor) for tunnel
application was assessed using RocLab© software and Table 5.2.5 is a summary of the
results:
Table 5.2.5. The rock mass strength in the Lower Asmari unit.
Hoek-Brown Classification
sigci
116 MPa
GSI
59
mi
9
D
0
Hoek-Brown Criterion
mb
2.1
s
0.01
a
0.5
Hoek-Brown Classification
sigci
138 MPa
GSI
71
mi
9
D
0
Hoek-Brown Criterion
mb
3.2
s
0.04
a
0.5
Failure Envelope Range
Application Tunnels
sig3max 0.7
MPa
Unit Weight 0.03 MN/m3
Tunnel Depth
50 m
Mohr-Coulomb Fit
c
1.6 MPa
phi (ϕ) 57.5°
Rock Mass Parameters
sigt
-0.6 MPa
sigc
11.7 MPa
sigcm 23.6 MPa
Em 16788 MPa
Failure Envelope Range
Application Tunnels
sig3max 0.7
MPa
Unit Weight 0.03 MN/m3
Tunnel Depth
50 m
Mohr-Coulomb Fit
c
3.96
MPa
phi (ϕ) 57.6°
Rock Mass Parameters
sigt
-1.7
MPa
sigc
27.4
MPa
sigcm 38.4 MPa
Em 33496.5 MPa
411
Figures 5.2.3 and 5.2.4 indicate the relasionship between major and minor principal stresses
also normal and shear stresses for the Hoek-Brown and equivalent Mohr-Coulomb criteria for
GSI 59 and 71.
Structural Stability Control and Rock Support Arrangement elements were determined by
using the RocScience Software UNWEDGE©.
Four major discontinuity planes (Table 5.2.1) control, shape and dimensions of the rock
wedges in the diversion tunnel.
Normal Stress vs. Shear Stress
Principal Stresses
7
6
Shear stress (MPa)
Major principal stress (MPa)
25
20
15
10
5
5
4
3
2
1
0
0
-1
-0.5
0
0.5
-1
1
0
Hoek-Brown
1
2
3
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.2.3. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 59 in the lower unit of the Asmari Formation.
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
40
12
10
Shear stress (MPa)
35
30
25
20
15
10
8
6
4
2
5
0
0
-2
-1.5
-1
-0.5
0
0.5
-3
1
-1
0
1
2
3
4
5
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
-2
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.2.4. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 71 in the lower unit of the Asmari Formation.
Unwedge© program always initially calculates the maximum sized wedges which can
form around an excavation (Figure 5.2.5). Wedges can scale down according to actual field
observations (e.g. observed joint trace lengths, persistence and wedge volume). The Js1
(bedding planes), Js2, and Js3 intersecting discontinuities play a principal role in wedge
failure in the diversion tunnel. The safety factor, volume, dimensions, wedge weight, wedge
length, excavation face area and sliding direction of all wedges have been introduced in Table
5.2.6.
414
Figure 5.2.5 is a multi view of the Karun-3 dam diversion tunnel showing typical wedges
which can be formed in the roof, sidewalls and floor by joint sets Js1(bedding plane), Js2 and
Js3. This figure represents approximately real possible sizes of wedges, which can be formed
in the tunnel. Of course, during construction, decision on the sizes of wedges should be
scaled and revised according to the real joint trace lengths measured during the excavation
operation.
In Figure 5.2.5 it is evident that the two roof wedges (upper left and upper right) are
relatively unstable and they need to be stabilized. The factor of safety is about 1.7 during
excavation. The stabilization is achieved by the placement of 4.5 m length bolting system of
20 mm diameter, with 2.5 m spacing and 25 mm shotcrete layers in crown and sides.
Figure 5.2.5. Multi view of the diversion tunnel. The shape, dimensions and
specifications of wedges because of intersecting major discontinuity sets Js.1 (bedding
planes), Js.2 and Js.3 in diversion tunnel at the Karun-3 Dam.
Dimensions on the number, length and capacity of the rock bolts are made by on-site
geotechnical staff using equilibrium calculations based on the volume of the wedges defined
by the measured trace lengths. For those wedges which involve sliding on one plane or along
the line of intersection of two planes, rock bolts are installed across these planes to bring the
sliding factor of safety of the wedge up to 1.5. For wedges which are free to fall from the
roof, a factor of safety of 2 is used. This factor is calculated as the ratio of the total capacity
of the bolts to the weight of wedge and is intended to account for uncertainties associated
with the bolt installation. Early recognition of the potential instability problems, identification
and visualization of the wedges which could be released and the installation of support at
each stage of excavation, before the wedge bases are fully exposed, resulted in a very
effective stabilization program (Unwedge©Rocscience Inc, 2004).
The factor of safety after installation of 4.5 m rock bolts and 25 mm shotcrete increased to
2.3 and 3.3 respectively (Figure 5.2.6).
412
Rock support arrangement in diversion tunnel, can be introduced according to Table 3.4. The
support elements are converted for 15 m excavated span (Figure 5.2.6).
-Bolt length – 4.50 m in crown, and in sides if required
-Spacing – 2.50 m
-Shotcrete – 25.0 mm in crown, and in sides if required
B
A
Figure 5.2.6. Rock support arrangement in good quality rock mass at 15 m excavated
diameter of diversion tunnel (A- 2D and B- 3D views).
Table 5.2.6. The rock wedge specifications at the diversion tunnel resulted by Js.1, Js.2
and Js.4.
Floor wedge [3]
Factor of Safety: stable
Wedge Volume: 93.4 m3
Wedge Weight: 252.2 tones
Wedge z-Length: 22. 9 m
Excavation Face Area: 157.3 m2
Upper Left wedge [4]
Factor of Safety: 1.8
Wedge Volume: 13.2 m3
Wedge Weight: 35.6 tones
Wedge z-Length: 10.9 m
Excavation Face Area: 26.7 m2
Sliding Direction (trend, plunge): 47°, 85°
Lower Right wedge [5]
Factor of Safety: 15.9
Wedge Volume: 0.2 m3
Wedge Weight: 0.6 tones
Wedge z-Length: 1.3 m
Excavation Face Area: 2.4 m2
Sliding Direction (trend, plunge): 180°, 8°
Upper Right wedge [6]
Factor of Safety: 1.8
Wedge Volume: 79 m3
Wedge Weight: 213.3 tones
Wedge z-Length: 15.7 m
Excavation Face Area: 67.6 m2
Sliding Direction (trend, plunge): 135°, 81°
Roof wedge [8]
Factor of Safety: 0.0
Wedge Volume: 0.001 m3
Wedge Weight: 0.002 tones
Wedge z-Length: 0.7 m
Excavation Face Area: 0.2 m2
Sliding Direction (trend, plunge): 0°, 90°
The finite element mesh shown in Figure 5.2.7 is constructed to simulate the loading
conditions of normal and shear stress and their distribution on all wedge blocks. Except for
(Js1, Js2, and Js3) other discontinuity sets have less influence on instability in the tunnel. All
possible wedges are shown in Figure 5.2.7. The wedges shown in C-D, E-F and G-H are
considered more stable than the case A-B because smaller blocks are involved, and light
support such as primary reinforced shotcrete effectively limit failure.
413
A
B
C
D
E
F
G
H
Figure 5.2.7. The finite element mesh of normal and shear stresses for all possible wedge
because of intersection of discontinuities at diversion tunnel. The critical wedges based on
distribution of shear stress and the shapes of wedges are A-B. In the other cases, the
instabilities will be very small and local. A-B (Js.1, Js.2, Js.3), C-D (Js.1, Js.2, Js.4), E-F
(Js.1, Js.3, Js.4), G-H (Js.2, Js.3, Js.4).
411
5.2.2. Hydropower Tunnels
5.2.2.1. Lower Asmari (4a1, 4a2, 4a3, 4a4)
Geological data for the tunnels were defined from surface mapping and four boreholes,
namely, BH-108C, BH-111B, BH-118M, BH-120V and BH-107T. The detailed geology
along the power tunnels are shown in Figure 5.2.8.
The tunnels are constructed from 0.0 m (intake) to 465 m in the Pabdeh Formation, and
Elevation (m)
Legend:
Gachsaran F. (5a): evaprates
1000.0
960.0
920.0
BH-108C
BH-111B
BH-118M
BH-120V
880.0
U. Asmari (4b)
limestone and marl
L. Asmari (4a1, 4a2, 4a3, 4a4)
limestone, dolomite
Pabdeh (3b): marl
840.0
800.0
BH-107T
760.0
720.0
4a1
680.0
4a2
4a3
4a4
3b
640.0
0.0
80.0
160.0
240.0
320.0
400.0
480.0
560.0
600.0
Figure 5.2.8. Geological section along the hydropower tunnels axis and gate shaft (after MG co., 1993).
from 465 m to 950 m (outlet) in the Asmari Formation. The Pabdeh Formation along the
tunnel alignment comprises fair to good quality rock. Weighted mean RQDs range from 60%
to 80%. The rock is generally moderately strong to strong and hydraulic conductivity is fairly
low.
The downstream portion of the high pressure tunnels, the gate shafts and penstocks are
excavated in the Asmari Formation. From 465 m to 695 m the underground works are
predominantly limestone beds of subunits 4a1, 4a2 and 4a3. Between 695 m and 950 m
(outlet), marly limestone and limestone with minor marlstone of subunit 4a4 is encountered.
All the subunits are made up of strong to very strong rock which is of fair to good rock
quality. Weighted RQDs generally ranged from 60% to 80%. A few zones of closely
fractured to fragmented rock have noted, the most notable being the 10 to 20 m wide, so
called vuggy zone at approximately St. 550 m. Rock mass hydraulic conductivities are high,
generally ranging from 1x10-4 to 1x10-3 cm/s.
Based on discontinuity surveys (Figure 5.2.9) which have been taken along the tunnel
route, the following significant discontinuity sets have been identified (Table 5.2.7). Spacing
of bedding discontinuities and for the joint sets is wide to very wide (0.6 to 2 m). From 0.0 m
to approximately 450 m, the tunnels pass through the dome of the Keyfe Malek Anticline. In
this section the bedding dip is almost horizontal. Downstream from 450 m the tunnels are
415
located in the southwest flank of the anticline and the bedding is inclined at 70° to 85° toward
the southwest.
Table 5.2.7. Summary of discontinuity data at the Hydropower tunnels.
Discontinuity Set
Bedding
Set A
Set B
Dip Direction (°)
224
128
325
Dip (°)
85
80
32
Figure 5.2.9. Contour plot and major plane plots of discontinuity sets at the hydropower tunnels
(Dips©, equal area projection-Schmidt net, lower hemisphere).
The RMR value for the Lower Asmari (units 4a1, 4a2, 4a3, 4a4) based on Table 3.3 in
hydropower tunnel are assessed as follows:
Table 5.2.8. Assessment of Rock Mass Rating for the Lower Asmari Formation (4a1, 4a2,
4a3, 4a4) in the hydropower tunnels.
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition discontinuities
Ground water
Adjustment for joint orientation
Value
138 - 116
80% - 60%
B, 0.6-6.0m – j, 2- 0.6
Slightly rough slightly weathered
Wet to Dripping
Fair
Total : 64 to 71 (Good)
Rating
12 - 12
17 - 13
15 - 15
25 - 25
7-4
-5
Based on Table 3.4 the guidelines for excavation and support of a 10 m span rock tunnel for
the above RMR values are as follow:
Table 5.2.9. Rock support types for units 4a1, 4a2, 4a3 and 4a4 in the hydropower tunnels.
Rock mass
class
II – Good rock
Excavation
Full face, 1- 1.5 m advance.
Complete support 20 m
from face
Rock bolts (20 mm diameter,
fully grouted)
Locally, bolts in crown 3 m
long, spaced 2.5 m with
occasional wire mesh
416
Shotcrete
50 mm in crown where
required
Steel sets
None
The Stand up Time for the hydropower tunnel with 15 m diameter was assessed based on the
Bieniawski stand up time graph as 2×103 hours (83 days) for RMR (71) and 8×102 hours (33
days) for RMR (64).
The Rock Tunneling Quality Index, Q was determined as 35.1 (Good Quality) and 115.1
(Extremely Good Quality)
The GSI was determined from Hoek and Brown (1997) using equations 3.11, 3.12, and 3.13:
The GSI is then between 59 and 66.
Structural Stability Control and Rock Support Arrangement elements were determined by
using the RocScience Software UNWEDGE©.
The three major discontinuity planes (Table 5.2.7) that control the shape and dimensions
of wedges in the circular section of the power tunnels are presented in Figure 5.2.10.
The wedge information and specifications are summarized in Table 5.2.10. Rock support
arrangement for good quality rock mass (4a1, 4a2, 4a3, 4a4) in the hydropower tunnel, can be
introduced based on Table 3.4. Then the support elements are converted for a 15 m excavated
span (Figure 5.2.11).
Figure 5.2.10. The shape dimensions and specifications of wedges because of intersecting
major discontinuities in the hydropower tunnel at Karun-3 Dam (dia.15 m).
-Bolt length – 4.50 m in crown, and in sides if required
-Spacing – 2.5 m
-Shotcrete – 25.0 mm in crown, and in sides if required
417
Table 5.2.10. The rock wedge specifications in the hydropower tunnel resulting from three joint sets.
Lower Right wedge [1]
Factor of Safety: stable
Wedge Volume: 20.7 m3
Wedge Weight: 55.9 tonnes
Wedge z-Length: 9.1 m
Excavation Face Area: 21.7 m2
Upper Right wedge [2]
Factor of Safety: 12.1
Wedge Volume: 2 m3
Wedge Weight: 5.4 tonnes
Wedge z-Length: 4.7 m
Excavation Face Area: 6.2 m2
Sliding Direction (trend, plunge): 159°, 78°
Roof wedge [4]
Factor of Safety: 9.3
Wedge Volume: 0.1 m3
Wedge Weight: 0.3 tonnes
Wedge z-Length: 1.7 m
Excavation Face Area: 1.3 m2
Sliding Direction (trend, plunge): 224°, 85°
Floor wedge [5]
Factor of Safety: stable
Wedge Volume: 0.1 m3
Wedge Weight: 0.3 tonnes
Wedge z-Length: 1.7 m
Excavation Face Area: 1.3 m2
Sliding Direction (trend, plunge): 40°, 9°
Lower Left wedge [7]
Factor of Safety: 13
Wedge Volume: 2 m3
Wedge Weight: 5.4 tonnes
Wedge z-Length: 4.7 m
Excavation Face Area: 6.2 m2
Sliding Direction (trend, plunge): 325°, 32°
Upper Left wedge [8]
Factor of Safety: 1.4
Wedge Volume: 21 m3
Wedge Weight: 55.9 tonnes
Wedge z-Length: 9.1 m
Excavation Face Area: 21.7 m2
Sliding Direction (trend, plunge): 2°, 64°
A
B
Figure 5.2.11. Rock support arrangement A (2D view) and B (3D view) of the Lower Asmari
Formation (4a1, 4a2, 4a3, 4a4) in good quality rock mass in 15 m diameter at the power
tunnel.
5.2.2.2. Unit- As.2 (Upper Asmari Formation- 4b)
Based on lithological column, the unit consists of 200 m thin to medium bedded marly
limestone, marlstone, shale and limestone. The limestone and marly limestone are light grey
to grey, fine to medium grained, crystalline, medium to thickly bedded and strong to very
strong. The shale and marlstone are grey to dark grey, fine grained, thinly to thickly bedded
and medium strong. Petrographical analysis indicated the limestone classified as
Intrabiomicrite to Biomicrite- mudstone to wackestone. The bioclasts consist of mainly
planktonic foraminifera such as Globigerina sp., some benthic species such as Borelis sp.,
Dendritina sp., Miogypsina sp., and miliolides in addition Bivalves and Echinoid shell
fragments. The porosity is mainly due to fractures and the values generally are between 1% to
13.8% which indicate medium to extremely high porosity.
The discontinuities are open at surface and have close to moderate spacing. Rock blocks
are usually small to medium sized tabular fragments. Frequent calcite veins up to 10 mm
418
thick, are present in most locations. Rock quality is variable with the weighted mean RQD
values ranging from 31% to 81% which indicates poor to good quality rock mass.
If the discontinuity data from the dam in addition to the RMR parameters for the upper unit
are taken into account the rock mass rating can be assessed as in Table 5.2.11.
Table 5.2.11. Assessment of Rock Mass Rating for the Upper Asmari (As.2).
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition discontinuities
Ground water
Adjustment for joint orientation
Value
15- 116
31% - 53%
0.2- 0.6, 0.6- 2
Slightly rough slightly weathered
Wet to Dripping
Fair
Total : 44 to 67 (Good)
Rating
2 - 12
8 - 13
10 - 15
25 - 25
4-7
-5
The Rock Quality Index, Q can then be calculated indirectly from equation 3.10 (Rutlege,
Preston, 1978):
Then the Q values fall between 1.2 (Poor Quality) and 58.4 (Very Good Quality).
The geological strength index (GSI) was calculated according to Hoek and Brown, 1997,
(3.11 and 3.12):
The GSI values vary between 39 and 62.
The rock mass strength with input data, UCS, GSI, mi and D for general application was
assessed using RocLab© software and Table 5.2.12 is a summary of the results:
Table 5.2.12. The rock mass strength in the Upper Asmari unit.
Hoek-Brown Classification
sigci
15 MPa
GSI
39
mi
7
D
0
Hoek-Brown Criterion
mb
0.8
s
0.001
a
0.5
Hoek-Brown Classification
sigci
116 MPa
GSI
62
mi
8
D
0
Hoek-Brown Criterion
mb
2.1
s
0.01
a
0.50
Failure Envelope Range
Application General
sig3max 3.8
MPa
Mohr-Coulomb Fit
c
0.6 MPa
phi (ϕ) 24.4°
Rock Mass Parameters
sigt -0.02
MPa
sigc
0.5
MPa
sigcm 1.7
MPa
Em 2056.1
MPa
Failure Envelope Range
Application General
sig3max 29
MPa
Mohr-Coulomb Fit
c
6.7 MPa
phi (ϕ) 32.1°
Rock Mass Parameters
sigt
-0.8
MPa
sigc
13.9
MPa
sigcm 24.7
MPa
Em 19952.6 MPa
419
Figures 5.2.12 and 5.2.13 show the relationship between major and minor principal
stresses in addition to normal and shear stresses for Hoek- Brown and Mohr- Coulomb
criteria for GSI 39 and GSI 62 in the upper unit of the Asmari Formation.
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
12
3.5
3
Shear stress (MPa)
10
8
6
4
2
2.5
2
1.5
1
0.5
0
0
-1
0
1
2
3
-1
4
0
1
2
Hoek-Brown
3
4
5
6
7
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.2.12. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 39 in the upper unit of the Asmari Formation.
With consideration of all geological strength index values (GSI) for the two rock units of
the Asmari Formation, which resulted in the above calculations, the situation of rock mass
strength at the Karun-3 dam can be plotted on Figure 5.2.14. Figure 5.2.14 has been used to
estimate the value of GSI from field observations of blockiness and discontinuity surface
conditions.
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
140
45
40
35
30
25
20
15
10
5
0
Shear stress (MPa)
120
100
80
60
40
20
0
-5
0
5
10
15
20
25
30
35
Hoek-Brown
-10
0
10
20
30
40
50
60
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.2.13. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 62 in the upper unit of the Asmari Formation.
451
Figures 5.2.14 and 5.2.15, based on the strength and other engineering rock mass properties
for the Asmari Formation at the Karun-3 dam, show the rock mass quality variations are wide
ranging from Blocky-Very Well Interlocked and Good (B/G) to Blocky Disturbed /Seamy and
Fair (BD/F).
Figure 5.2.14. General Geological Strength Index (GSI) chart, for jointed
rock masses (Hoek and Brown 1997, Hoek and Karzulovic, 2001). The
shaded area is indicative of distribution of geological strength index of
various rock mass units of the Asmari Formation at the Karun-3 dam.
454
ASMARI FORMATION
615.0 m
Figure 5.2.15. The lithological units and engineering rock mass characterization of the Asmari
Formation at the Karun-3 dam.
452
5.2.3. Hydrogeology of Project Site
Records of river levels during the feasibility study period show that there is a close
relationship between groundwater level fluctuations and seasonal changes in river level.
Water level elevations in Boreholes BH-101A, BH106D, BH107E, BH110-F, BH114U and
BH-116S are generally within 1 m of river elevation. These boreholes are all adjacent to the
river. The abutments at the damsite are well drained which indicates that the local hydraulic
conductivity is high. Borehole BH-108C was drilled in the Pabdeh Formation and is located
230 m away from the river. It has a water elevation that is 3 m to 5 m higher than the
corresponding river elevation. The groundwater table was not encountered in boreholes BH115Z and BH-119CA, both of which were terminated well above river level (MG.co. 1998).
5.2.3.1. Hydraulic Conductivity
Results of water pressure tests (lugeon test) in drill holes were evaluated in terms of
coefficient of permeability (k). At later stages, the Lugeon criterion was introduced and the
coefficient of infiltration was calculated. The coefficient of permeability (k) of the bedrock
varies from 9x10-7 to 6x10-2 cm/s.
In the Asmari Formation, a large number of measurements indicate k values in the range from
2x10-3 to 4x10-4 cm/s and in the marlstone of the Pabdeh Formation between 3x10-5 to 8x10-5
cm/s (Table 5.2.13).
Table 5.2.13. Permeability (K) values classification.
Very Low K
Low K
Medium K
High K
< 10-5 cm/s (about 1 lugeon)
10-5 to 10-4 cm/s (about 1 to 10 lugeon)
10-4 to 10-3 cm/s (about 10 to 100 lugeon)
> 10-3 cm/s (about 100 lugeon)
In all studies, k values were related directly to permeability. Similarly, arbitrary subdivisions
of calculated Lugeon values (coefficient of infiltration) were made to indicate zones of high
and low permeability. The groupings given in Table 5.2.14 are used only for comparative
descriptions.
Table 5.2.14. Hydraulic conductivity of the Asmari and Pabdeh formations in the Karun-3 Dam.
Hydraulic Conductivity (K) %
Asmari F.
Unit 4b (78tests above 100m depth)
Unit 4a (556 tests above 100m depth)
Unit 4a (479 tests below 100m depth)
Pabdeh F.
Unit 3 (226 tests from 0 to 250m
depth
very Low
Low
Medium
High
4
9
15
6
13
23
11
23
35
79
55
27
26
18
19
37
The Lugeon values indicate great variation in hydraulic conductivity with depth and
location. Generally in the Asmari Formation to a depth of 100 m from the surface, the
hydraulic conductivity varies from very low to high with the majority of the results in the
medium range. Below this depth, the measured conductivities are very low to medium.
453
5.2.3.2. Curtain Grouting
The extent of curtain grouting is indicated in Figure 5.2.16. Grout curtains are critical
components of dams constructed on karstic bedrock foundations such as at Karun-3 damsite.
In this geological environment, grout curtains are more extensive and require much higher
volumes of cement than is normally the case in other rock types. The grout curtain should
extend 150 m below the base of the dam and 200 m into each abutment.
A multiline curtain, comprising 2 to 3 rows of holes, was installed in the medium to high
permeability limestone in each abutment and beneath the dam. High grout takes were
anticipated in this part of the grout curtain. A single row curtain with relatively low grout
take was extended through the slightly permeable rock units near the right abutment and
below 100 m depth under the base and left abutment.
The grouting was performed mostly from tunnel galleries, the arrangement of which is
shown on Figure 5.2.16. The grout galleries are 3.5 m high by 2.5 m wide, based on the
anticipated size of drilling equipment. Grout holes should be approximately 50 mm in
diameter and have an average spacing of 3 m, although spacings as low as 1.50 m can be
expected at some locations.
Figure 5.2.16. Developed section of the grout curtain at the Karun-3 dam (MG co. 1989).
5.2.4. Watertightness of Reservoir
The reservoir is aligned parallel to the bedrock structures. Seepage through the sides or
bottom of the reservoir will be perpendicular or oblique to the bedding. In the northwestern
end of the reservoir, seepage would be parallel to the bedding through rock formations
running to either sides of the dam. These two cases of reservoir seepage are discussed
separately in the following paragraphs.
The rocks of the Agha Jari and Gachsaran Formations, which make up most of both flanks
and the bottom of the reservoir, have low to very low permeability. Boreholes BH-102K and
BH-103J, which were drilled in the Gachsaran Formation, indicate that permeabilities of the
451
mudstones, marlstone and anhydrites are generally less than 1x10-5 cm/s. High hydraulic
conductivities in the order of 2x10-4 cm/s to 1x10-3 cm/s were found in sandstone strata. As
flow is mostly across strike, the less permeable argillaceous and anhydrite rocks will
determine the overall mass hydraulic conductivity. Slightly southwest of the reservoir, the
marlstone, shales and limestones of the Pabdeh Formation are warped up well above the
reservoir elevation of 850 m. Testing at the dam site has shown that the hydraulic
conductivity perpendicular to bedding in the Pabdeh Formation is low, and generally ranges
between 1x10-5 cm/s - 1x10-4 cm/s.
Reservoir seepage through the low permeability rocks of the Gachsaran and Agha Jari
Formations will be very slight. These rocks outcrop along the entire right bank and bottom of
the reservoir upstream from Pole Shalu. It is possible that windows below elevation 850 m
pass through the Gachsaran Formation beneath the displaced rock masses. If this is the case,
the low permeability rocks of the nearby Pabdeh Formation will contain potential leakage
from the left flank of the reservoir (MG. co, 1989).
455
5.3. Engineering Geological Characteristics of the Karun-4 Dam and Power plant
(Engineering Rock Mass Classification of the Asmari Formation)
5.3.1. Diversion Tunnel
5.3.1.1. Lower Unit (Lower Asmari Formation- As.1)
In order to divert the Karun River during the dam construction, two tunnels in the right
flank have been designed. The tunnels are excavated at a strike of S40W with lengths of 610
m and 635 m respectively and diameter of 11.2 m. Almost 50% of the tunnel's length are
excavated in the Pabdeh Formation and the rest pass through the Asmari Formation (As.1).
The Asmari Formation (As.1), which forms the dam abutments, is considered here to be a
part of the bedrock of this structure. This part is composed of thick limestone beds, porous
limestone (karstified) with intercalations of marly limestone (Figures 5.3.1 and 5. 3.2).
D/S Cofferdam
Figure 5.3.1. The diversion tunnel at outlet and down stream coffer dam, during the heavy flood 2006 (left).
Diversion tunnel with temporary support elements. The final reinforced concrete lining has been done in the
lower part of tunnel (right).
The Asmari Formation (As.1) along the diversion tunnel is fair to good quality limestone
with RQD generally ranging between 55% to 83%.
The RMR value for unit As.1 based on rock mass rating parameters in Table 3.3 can be
assessed as in Table 5.3.1.
Table 5.3.1. Major discontinuity sets and their specifications.
Discontinuity Set
Set 1
Set 2
Set 3
Dip direction (°)
55
092
126
Dip (°)
42
65
85
Bedding
230
49
Spacing
0.6- 2 m
0.6- 2 m
0.6- 2 m
456
Surface
rough
rough
smooth
smooth to
rough
Opening
2- 5 mm
2- 4 mm
2- 5 mm
Filling
calcite/clay
calcite/clay
calcite/clay
Length
3- 15 m
5- 10 m
3- 30 m
2- 100 mm
calcite/clay
>100 m
Elevation (m)
Figure 5.3.2. The engineering geological section along the diversion tunnel. This tunnel with over 600 m
excavated in the Pabdeh and lower unit of Asmari Formations (after MG co., 1989).
Table 5.3.2. Assessment of Rock Mass Rating for the Asmari Formation (Lower unit).
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition of discontinuities
Ground water
Adjustment for joint orientation
Value
48- 100
55% - 83%
0.6- 2m
Rough to Smooth
Wet to Dripping
Very favorable
Rating
4- 7
13- 17
15
25
4- 7
0
Total : 61– 71 (Good)
In addition, based on Table 3.4, the guidelines for excavation and support of an 11.2 m
diameter tunnel for relevant RMR values are as follows (Table 5.3.3):
Table 5.3.3. Rock support types in the diversion tunnel.
Rock mass
class
II – Good rock
Excavation
Full face, 1- 1.5 m advance.
Complete support 20 m
from face
Rock bolts (20 mm diameter,
fully grouted)
Locally, bolts in crown 3m
long, spaced 2.5m with
occasional wire mesh
Shotcrete
30 mm in crown where
required
Steel sets
Non
The Stand up Time for the diversion tunnel is 2×103 hours (83 days) for a good quality rock
mass based on the Bieniawski stand up time graph.
The Rock Tunneling Quality Index, Q considering the six parameters in Table 3.6, can be
determined based on equation 3.4.
Or can be calculated by emprical equation 3.10 introduced by Rutlege and Preston (1978).
The Q values were determined as 21 (Good Quality) and 151 (Extremely Good Quality).
Structural Stability Control and Rock Support Arrangement elements were determined by
using the RocScience Software UNWEDGE©.
457
There are four major discontinuities (Table 5.3.1) which control the shape and dimensions
of wedges in the diversion tunnel. Three of them have more influence on the instabilities and
are, Js1, Js3 and bedding planes (Js.4).
Figure 5.3.3 and Table 5.3.4 show the safety factor, volume, dimensions, geometry, wedge
weight, wedge z length, excavation face area and sliding direction of the rock wedges.
A
B
C
D
Figure 5.3.3. All possible rock wedges due to intersection of the major joint sets, Js.1,
Js.3 and bedding planes in the diversion tunnel. A- Perspective view, B- Side view of
tunnel showing unstable wedges, C- (2D view) and D (3D view) of the Rock support
arrangement of the lower Asmari Formation in good quality rock mass.
Wedge 8 is the only unstable block of 6.6 m3 with a factor of safety of 1.1. If wedge
sliding takes place, the direction of sliding will be 330°/ 55º. Other blocks are regarded as
relatively stable during the excavation operation. After installation of support elements as
stated below, the safety factor of wedge no. 8 increases to 3.14.
Figure 5.3.4 shows the finite elements mesh of normal and shear stresses for all possible
wedges because of intersection of discontinuities in the diversion tunnel and Table 5.3.4
indicates wedges specifications. The critical wedges based on distribution of shear stress can
be observed. Intersection of Js.1, Js.3 and bedding planes (A, B), intersection of Js.2, Js.3 and
bedding planes (C, D), intersection of Js.1, Js.2 and Js.3 (E, F).
-Bolt length – 3.0 m Ф20.0 mm, in crown, and in sides locally if required
-Spacing – 2.5 m
-Shotcrete – 30.0 mm primary in crown, and in sides 20 mm if required
458
A
B
C
D
E
F
Figure 5.3.4. The finite elements mesh of normal and shear stresses for all possible
wedges because of intersection of discontinuities in the diversion tunnel.
The geological strength index (GSI) based on two equations (3.11 and 3.12) which were
introduced by Hoek and Brown (1997) was calculated as follows:
The GSI values vary between 56 and 66.
The rock mass strength with input data, UCS, GSI, mi, D and tunnel depth was assessed
using RocLab© software and Table 5.3.5, Figures 5.3.5 and 5.3.6 are the summary of the
results.
459
Table 5.3.4. The rock wedge specifications in the diversion tunnel.
Excavation Face Area: 0.1 m2
Shear Force: 0.0 tonnes
Sliding Direction (trend, plunge): 40°, 41°
Lower Right wedge [1]
Factor of Safety: stable
Wedge Volume: 4 m3
Wedge Weight: 10.8 tonnes
Wedge z-Length: 8.0 m
Excavation Face Area: 15.6 m2
Shear Force: 0.5 tonnes
Sliding Direction (trend, plunge): 142°, 3°
Lower Left wedge [3]
Factor of Safety: stable
Wedge Volume: 14.5 m3
Wedge Weight: 39.2 tonnes
Wedge z-Length: 10.3 m
Excavation Face Area: 27.1 m2
Shear Force: 0.0 tonnes
Upper Left wedge [4]
Factor of Safety: stable
Wedge Volume: 0.0 m3
Wedge Weight: 0.001 tonnes
Wedge z-Length: 0.8 m
`
Upper Right wedge [6]
Factor of Safety: 4.4
Wedge Volume: 16.2 m3
Wedge Weight: 43.7 tonnes
Wedge z-Length: 10.3 m
Excavation Face Area: 23 m2
Shear Force: 43.6 tonnes
Sliding Direction (trend, plunge): 126°, 85°
Upper Left wedge [8]
Factor of Safety: 1.1
Wedge Volume: 6.6 m3
Wedge Weight: 17.8 tonnes
Wedge z-Length: 7.1 m
Excavation Face Area: 14.3 m2
Shear Force: 0.00 tonnes
Sliding Direction (trend, plunge): 330°, 55°
Table 5.3.5. The rock mass strength in the Lower Asmari unit.
Hoek-Brown Classification
sigci
100 MPa
GSI
66
mi
8
D
0
Hoek-Brown Criterion
mb
2.4
s
0.02
a
0.5
Failure Envelope Range
Application
Tunnels
sig3max 1.4 MPa
Unit Weight 0.03 MN/m3
Tunnel Depth 100 m
Mohr-Coulomb Fit
c
2.3 MPa
phi (ϕ) 53.1°
Rock Mass Parameters
sigt -0.9
MPa
sigc 15.02
MPa
sigcm 23.1
MPa
Em 25118.9 MPa
Hoek-Brown Classification
sigci
48 MPa
GSI
56
mi
8
D
0
Hoek-Brown Criterion
mb
1.7
s
0.01
a
0.5
Failure Envelope Range
Application Tunnels
Unit Weight 0.02 MN/m3
Tunnel Depth 100 m
Mohr-Coulomb Fit
c
0.8 MPa
phi (ϕ) 47.9°
Rock Mass Parameters
sigt -0.2 MPa
sigc 4.1
MPa
sigcm 8.6
MPa
Em 9786.4 MPa
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
14
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Shear stress (MPa)
12
10
8
6
4
2
0
-0.5
0
0.5
1
1.5
Hoek-Brown
-1
0
1
2
3
4
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.3.5. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 56 in the lower unit of the Asmari Formation.
461
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
30
10
9
8
7
6
5
4
3
2
1
0
Shear stress (MPa)
25
20
15
10
5
0
-1.5
-1
-0.5
0
0.5
1
1.5
2
-2
-1
0
Hoek-Brown
1
2
3
4
5
6
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.3.6. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 66 in the lower unit of the Asmari Formation.
5.3.1.2. Middle Unit (Middle Asmari Formation- As.2)
This unit lithologicaly comprise medium to thickly bedded limestone, marlylimestone and
marlstone with, dolomitization well developed at the base slightly karstified with mostly
fractured and vuggy porosity. The rock is impermeable but can be locally very high
pemeability.
The RMR value for unit As.2 based on rock mass rating parameters in Table 3.3 can be
assessed as in Table 5.3.6.
Table 5.3.6. Assessment of Rock Mass Rating for the Middle Asmari Formation (Middle unit).
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition discontinuities
Ground water
Adjustment for joint orientation
Value
39- 116
53% - 84%
0.6- 2.0 m
Rough to Smooth, weathered
Damp
Very unfavorable
Total : 32– 49 (Weak to fair)
Rating
4-12
13- 17
10- 15
20
10
-25
The Rock Quality Index (Q) can be clarified by two emprical equations 3.9 (Bieniawski,
1989) and 3.10 (Rutlege, Preston, 1978).
Based on Rotelech-Preston equation the Q values were determined as 0.84 - 2.8 (Poor
Quality).
The Geological Strength Index (GSI) was calculated using equations 3.11 and 3.12 (Hoek
and Brown, 1997) and the GSI values fall between 27 and 44.
The rock mass strength with input data, UCS, GSI, mi, D (disturbance factor) and tunnel
depth was assessed using RocLab© software and Table 5.3.7, Figures 5.3.7 and 5.3.8 are the
summary of the results.
464
Table 5.3.7. The rock mass strength in the Middle Asmari unit.
Hoek-Brown Classification
sigci
116 MPa
GSI
44
mi
8
D
0
Hoek-Brown Criterion
mb
1.1
s
0.002
a
0.5
Failure Envelope Range
Application General
sig3max
29 MPa
Hoek-Brown Classification
sigci
39 MPa
GSI
27
mi
8
D
0
Hoek-Brown Criterion
mb
0.6
s
0.0003
a
0.5
Failure Envelope Range
Application General
sig3max
9.8 MPa
Mohr-Coulomb Fit
c
4.9 MPa
phi (ϕ)
26.9°
Rock Mass Parameters
sigt -0.2 MPa
sigc 4.9
MPa
sigcm 15.9
MPa
Em 079.5 MPa
Mohr-Coulomb Fit
c
1.2 MPa
phi (ϕ)
2°
Rock Mass Parameters
sigt -0.02 MPa
sigc
0.5
MPa
sigcm 3.5
MPa
Em
61.6 MPa
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
30
8
7
Shear stress (MPa)
25
20
15
10
5
6
5
4
3
2
1
0
0
-2
0
2
4
6
8
10
-5
12
0
5
Hoek-Brown
10
15
20
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.3.7. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 27 in the middle unit of the Asmari Formation.
Normal Stress vs. Shear Stress
Principal Stresses
-5
35
30
Shear stress (MPa)
Major principal stress (MPa)
100
90
80
70
60
50
40
30
20
10
0
25
20
15
10
5
0
0
5
10
15
20
25
30
-10
35
Hoek-Brown
0
10
20
30
40
50
60
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.3.8. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 44 in the middle unit of the Asmari Formation.
462
5.3.1.3. Upper Unit (Upper Asmari Formation- As.3)
The upper Asmari Formation lithologically comprise marly limestone with marlstone and
sometimes interbedded limestone, non karstic to slightly karstified and impermeable to
locally very highly permeable.
Considering the discontinuity set specifications at the dam foundation, as well as the RMR
parameters for the upper unit, the rock mass rating can be assessed as in Table 5.3.8.
Table 5.3.8. Assessment of Rock Mass Rating for the Asmari Formation (Upper unit).
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition discontinuities
Ground water
Adjustment for joint orientation
Value
39-48
45% - 78%
0.6- 1.0 m
Rough to Smooth, weathered
Damp
Very unfavorable
Total : 32 – 41 (Weak to Fair)
Rating
4
8-17
15
20
10
-25
The Rock Quality Index (Q) can be assessed by two emprical equations (3.9 and 3.10) which
were introduced by (Bieniawski, 1989) and (Rutlege, Preston, 1978).
Based on Rotelech-Preston equation the Q values were determined as 0.15 to 0.7 (Very Poor
Quality).
The Geological Strength Index (GSI) was estimated according to equations 3.11 and 3.12
(Hoek and Brown, 1997) and the values obtained vary between 27 and 36.
The rock mass strength with input data, UCS, GSI, mi, D (disturbance factor) and tunnel
depth for general application was assessed using RocLab© software and Table 5.3.9, Figures
5.3.9 and 5.3.10 are the summary of the results.
Table 5.3.9. The rock mass strength in the Upper Asmari unit.
Hoek-Brown Classification
sigci
39 MPa
GSI
27
mi
8
D
0
Hoek-Brown Criterion
mb
0.6
s
0.0003
a
0.5
Failure Envelope Range
Application
General
sig3max 9.8 Mpa
Mohr-Coulomb Fit
c
1.2 MPa
phi (ϕ)
21.9°
Rock Mass Parameters
sigt
-0.02 MPa
sigc
0.5
MPa
sigcm
3.5
MPa
Em
1661.6 MPa
Hoek-Brown Classification
sigci
48 MPa
GSI
36
mi
8
D
0
Hoek-Brown Criterion
mb
0.8
s
0.001
a
0.5
Failure Envelope Range
Application
General
sig3max 12 MPa
Mohr-Coulomb Fit
c
1.8 MPa
phi (ϕ)
24.6°
Rock Mass Parameters
sigt
-0.04 MPa
sigc
1.2
MPa
si
5.5
MPa
Em 094.7
MPa
463
Figures 5.3.9 and 5.3.10 show the relationships between the major and minor principal
stresses and the normal and shear stresses for Hoek- Brown and Mohr- Coulomb criteria for
GSI 27 and GSI 36 in the upper unit of the Asmari Formation.
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
30
8
7
Shear stress (MPa)
25
20
15
10
5
6
5
4
3
2
1
0
0
-2
0
2
4
6
8
10
-5
12
0
Hoek-Brown
5
10
15
20
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.3.9. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 27 in the upper unit of the Asmari Formation.
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
40
12
10
Shear stress (MPa)
35
30
25
20
15
10
8
6
4
2
5
0
0
-2
0
2
4
6
8
10
12
14
0
5
10
15
20
25
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
-5
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.3.10. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 36 in the upper unit of the Asmari Formation.
Taking all geological strength index values (GSI) for the three rock units of the Asmari
Formation into account the rock mass strength at the Karun-4 dam is plotted in Figure 5.3.11.
Figures 5.3.11 and 5.3.12 are based on the strength and other engineering rock mass
properties for the Asmari Formation at the Karun-4 dam and show the rock mass quality
variations are wide ranging from Blocky- Very Well Interlocked and Good (B/G) to Blocky
Disturbed/Seamy and Fair (BD/F).
461
Figure 5.3.11. General Geological Strength Index (GSI) chart, for jointed
rock masses (Hoek and Brown 1997, Hoek and Karzulovic, 2001). The
shaded area is indicative of distribution of geological strength index of
various rock mass units of the Asmari Formation at the Karun-4 dam.
465
ASMARI FORMATION
500.0 m
Figure 5.3.12. The lithological units and engineering rock mass characterization of the
Asmari Formation at the Karun-4 dam.
466
5.4. Engineering Geological Characteristics of the Marun Dam and Power plant
(Engineering Rock Mass Classification of the Asmari Formation)
5.4.1. Diversion Tunnels
5.4.1.1. Lower Unit (Lower Asmari Formation- As.1)
The diversion tunnels are designed to pass a 1: 100 year flood of 4 000 m3/sec and include
a 45 m high upstream cofferdam with a volume of 42 1304 m3. The tunnel lengths are 505 m
and 640 m with diameters of 10.7 m and 13 m. They are orientated along strike of S33W,
almost perpendicular to the bedding strike which passes through all three units of the Asmari
succession.
The middle and upper Asmari units show some instability in the diversion tunnels due to the
influence of joint sets of 030°- 035°/75° and 300°/70°- 80° and some thin shale and marls
interbeds. The stabilization of these zones included rock bolts, wire mesh and shotcrete. In
some places, due to the intersection of joint sets and bedding planes, high leakage was
observed (Figure 5.4.1).
Figure 5.4.1. The Marun dam site and other accessory structures. The two diversion tunnels, power
tunnels, spillway at the left flank and rock fill dam body can be observed. The diversion and power
tunnels pass through all three units of the Asmari succession but the spillway structure is mainly
located in the lower and middle units.
The Asmari Formation (As.1) forms the lowest part of the bedrock and is composed of
grey to light grey massive to thickly bedded microcrystalline limestone and marly limestone
with thin interbeds of marls and shale. This unit is relatively karstified with low to medium
permeability. The porosity is 1.5% to 14.9 % indicating high to extremely high porosity for
this unit.
The rock quality designation (RQD) of the lower unit (As.1) is 70% to 85% that shows fair to
good quality rock mass. The uniaxial compressive strength tests and field tests (Schmidt
hammer test) indicate values ranging between 60 to 84 MPa.
The major discontinuity sets and their specifications are listed in Table 5.4.1.
467
Table 5.4.1. Major discontinuity sets and their specifications at the Marun dam site.
Discontinuity Set
Set 3
Set 4
Set 5
Set 6
Set 1 (Bedding)
DD.
209
296
033
207
033
Dip
74
88
79
54
34
Spacing
0.6- 2 m
0.6- 2 m
0.6- 2 m
0.6- 2 m
0.6-2, >2 m
Discon. surface
rough
rough
smooth
rough
Wavy , rough
Opening
10- 20 mm
2- 4 mm
2- 5 mm
2- 5 mm
2- 100
Filling
calcite/clay
calcite/clay
calcite/clay
calcite/clay
calcite/clay
Length
5- 10 m
5- 10 m
3- 30 m
5- 10 m
>100 m
The RMR value for the As.1 unit based on the rock mass rating parameters in Table 3.3 are
shown in Table 5.4.2.
Table 5.4.2. Assessment of Rock Mass Rating for the Asmari Formation (Lower unit).
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition of discontinuities
Ground water
Adjustment for joint orientation
Value
60- 84
70% - 85%
0.6- 2m, > 2 m
Rough to Smooth
Wet to Dripping
Very favorable
Rating
7
13- 17
15- 20
20- 25
4- 7
0
Total : 59– 76 (Fair to Good)
In addition, based on Table 3.4, the guidelines for excavation and support of a 13 m diameter
tunnel for the relevant RMR values are as follows (Table 5.4.3):
Table 5.4.3. Rock support types for the middle unit in the diversion tunnel (Bieniawski, 1984)
Rock mass
class
II – Good rock
III – Fair rock
Excavation
Full face, 1- 1.5 m advance.
Complete support 20 m
from face
Top heading and bench 1.53m advance in top heading.
Commence support 10 m
from face
Rock bolts (20 mm diameter,
fully grouted)
Locally, bolts in crown 3.5- 4 m
long, spaced 2.5 m, with
occasional wire mesh
Systematic bolts 3.5 – 4 m long,
spaced 2.5m in crown with wire
mesh, sides locally if needed
Shotcrete
Steel
sets
20 mm in crown where
required
Non
2Χ20mm in crown and 20 mm
in sides
Non
The Stand up Time for the diversion tunnel is 2×103 hours (83 days) for fair quality rock
mass and 1×104 hours (416 days) for good quality rock mass.
The Rock Tunneling Quality Index, Q can be determined from the parameters in Table 3.5
and equation 3.2 or experimentally can be calculated from the equations 3.9 or 3.10.
Based on the Rutlege-Preston (3.10) the Q values were determined as 15.1 (Good Quality)
and 268.6 (Extremely Good Quality).
Structural Stability Control and Rock Support Arrangement elements were determine by
using the RocScience Software UNWEDGE©.
Five major discontinuity planes (Table 5.4.1) control the shape and dimensions of wedges in
the diversion tunnels, but only three of them (Js.3, Js.4 and bedding planes) control the
instability (Figure 5.4.2).
468
A
B
C
D
Figure 5.4.2. The dimensions, geometry and structural specifications of wedges because
of intersecting major joint sets of Js.3, Js.4 and Js.1 (bedding planes) in the diversion
tunnel at the Marun dam. A- Perspective view, B- Side view of tunnel, showing
potentially unstable wedges and C- Rock support elements arrangement for the Asmari
Formation limestone.
The safety factor, volume, dimensions, geometry and other specifications of all possible rock
wedges in the diversion tunnels are listed in the wedge information and specifications in
Table 5.4.4.
Wedge 8 (upper left) is the only unstable rock wedge of 8.9 m3 with a factor of safety of
about 1.0. If wedge sliding occurred, the direction of sliding will be 139/55. Other blocks are
relatively stable during excavation operation. After installation of support elements (Table
5.4.4) the safety factor of wedge no. 8 increases to about 3.4.
The proposed stabilization elements are:
-Bolt length – 3.5 to 4 m, Ф20.0mm, in crown, and in sides locally if required
-Spacing – 2.5 m
-Shotcrete – 20.0mm primary in crown, and in sides 20 mm if required
The Geological Strength Index (GSI) was calculated based on equations 3.11 and 3.12.
The GSI values vary between 54 and 71.
469
Table 5.4.4. The rock wedge specification in the diversion tunnel
Floor wedge [1]
Factor of Safety: stable
Wedge Volume: 0.6 m3
Wedge Weight: 1.6 tonnes
Wedge z-Length: 0.8 m
Excavation Face Area: 4.2 m2
Lower Left wedge [3]
Factor of Safety: stable
Wedge Volume: 5.9 m3
Wedge Weight: 16.1 tonnes
Wedge z-Length: 6.04 m
Excavation Face Area: 16.6 m2
Sliding Direction (trend, plunge): 120°, 2°
Upper Left wedge [4]
Factor of Safety: 19.8
Wedge Volume: 0.003 m3
Wedge Weight: 0.01 tonnes
Wedge z-Length: 1 m
Excavation Face Area: 0.2 m2
Sliding Direction (trend, plunge): 209°, 74°
Lower Right wedge [5]
Factor of Safety: 80
Wedge Volume: 0.8 m3
Wedge Weight: 2.1 tonnes
Wedge z-Length: 6.8 m
Excavation Face Area: 7.9 m2
Sliding Direction (trend, plunge): 25°, 34°
Upper Right wedge [6]
Factor of Safety: 4
Wedge Volume: 14.7 m3
Wedge Weight: 39.7 tonnes
Wedge z-Length: 6.7 m
Excavation Face Area: 20.5 m2
Sliding Direction (trend, plunge): 296°, 88°
Upper Left wedge [8]
Factor of Safety: 1.1
Wedge Volume: 8.9 m3
Wedge Weight: 24.1 tonnes
Wedge z-Length: 8.8 m
Excavation Face Area: 15.7 m2
Sliding Direction (trend, plunge): 139°, 60°
A
B
C
D
Figure 5.4.3. The finite elements mesh of normal and shear stresses for all possible wedges
due to the intersection of discontinuities (Js.3, Js.4 and bedding planes at diversion tunnel.
Here the critical wedges based on distribution of shear stress can be observed with A- normal
stress distribution, B, C and D are shear stress distributions in perspective view, side view and
top view of tunnel respectively. The instability of wedge 8 can be observed in the top view.
The rock mass strength with input data, UCS, GSI, mi, D (disturbance factor) and tunnel
depth was assessed using RocLab© software and the results are summarized in Table 5.4.5,
Figures 5.4.4 and 5.4.5.
471
Table 5.4.5. The rock mass strength in the lower Asmari unit.
Hoek-Brown Classification
sigci
60 MPa
GSI
54
mi
8
D
0
Hoek-Brown Criterion
mb
1.5
s
0.006
a
0.5
Failure Envelope Range
Application Tunnels
sig3max
1.3 MPa
Unit Weight 0.03 MN/m3
Tunnel Depth
100 m
Mohr-Coulomb Fit
c 0.9
MPa
phi (ϕ) 48.9°
Rock Mass Parameters
sigt
-0.2
MPa
sigc
4. 6
MPa
sigcm 10.3
MPa
Em
9751.6 MPa
Hoek-Brown Classification
sigci
84 MPa
GSI
71
mi
8
D
0
Hoek-Brown Criterion
mb
2.8
s
0.04
a
0.5
Failure Envelope Range
Application Tunnels
sig3max
1.4 MPa
Unit Weight 0.03 MN/m3
Tunnel Depth
100 m
Mohr-Coulomb Fit
c
2.7 MPa
phi (ϕ) 52.5°
Rock Mass Parameters
sigt
-1.2
MPa
sigc
16.7
MPa
sigcm 22.4
MPa
Em 30700.1
MPa
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
16
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Shear stress (MPa)
14
12
10
8
6
4
2
0
-0.5
0
0.5
1
-1
1.5
0
1
Hoek-Brown
2
3
4
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.4.4. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 54 in the lower unit of the Asmari Formation.
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
30
10
9
8
7
6
5
4
3
2
1
0
Shear stress (MPa)
25
20
15
10
5
0
-1.5
-1
-0.5
0
0.5
1
1.5
-2
2
Hoek-Brown
-1
0
1
2
3
4
5
6
Normal stress (MPa)
Minor principal stress (MPa)
Mohr-Coulomb
Hoek-Brown
Mohr-Coulomb
Figure 5.4.5. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 71 in the lower unit of the Asmari Formation.
474
5.4.1.2. Middle Unit (Middle Asmari Formation- As.2)
The middle Asmari unit comprises lithologically of medium bedded microcrystalline
limestone, marly limestone and thin bedded marlstone frequency. This unit is relatively
karstified with low to medium permeability. The porosity is 1.4 to 11% indicating high to
extremely high porosity for this unit. The RQD of the middle unit (As.2) is 50% to 80% that
shows fair to good quality rock mass. Based on uniaxial compressive strength tests and field
tests (Schmidt hammer test) the UCS is between 35 to 95 MPa.
The RMR values based on rock mass rating parameters in Table 3.3 are assessed in Table
5.4.6.
Table 5.4.6. Assessment of Rock Mass Rating for the Asmari Formation (Middle unit).
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition of discontinuities
Ground water
Adjustment for joint orientation
Value
35- 95
50% - 80%
0.6- 2m,
Rough to Smooth
Wet to Dripping
Very favorable
Rating
4- 7
13- 17
15
20- 25
4- 7
0
Total : 56– 71 (Fair to Good)
The Rock Tunneling Quality Index, Q is calculated using empirical equation 3.10 (Rutlege,
Preston, 1978):
The Q values vary between 9.1 (Fair Quality) to 115.1 (Extremely Good Quality).
Table 5.4.7. The rock mass strength in the Middle Asmari unit.
Hoek-Brown Classification
sigci
35 MPa
GSI
51
mi
8
D
0
Hoek-Brown Criterion
mb
1.4
s
0.004
a
0.5
Failure Envelope Range
Application Tunnels
sig3max 1.3
MPa
Weight 0.03MN/m3
Tunnel Depth
100 m
Mohr-Coulomb Fit
c
0.6
MPa
phi (ϕ)
44.5°
Rock Mass Parameters
sigt
-0.1
MPa
sigc
2.2
MPa
sigcm
5.6
MPa
Em 6266.6
MPa
Hoek-Brown Classification
sigci
95 MPa
GSI
66
mi
8
D
0
Hoek-Brown Criterion
mb
2.4
s
0.02
a
0.5
Failure Envelope Range
Application Tunnels
sig3max 1.4
MPa
Unit Weight 0.03 MN/m3
Tunnel Depth
100 m
Mohr-Coulomb Fit
c
2.2
MPa
phi (ϕ)
52.9°
Rock Mass Parameters
sigt
-0.9 MPa
sigc
14.3
MPa
sigcm
22
MPa
Em 24482.8
MPa
The geological strength index (GSI) was calculated based on two simple equations 3.11 and
3.12 introduced by Hoek and Brown (1997) and the values obtained vary between 51 and 66.
472
The rock mass strength with input data, UCS, GSI, mi, D (disturbance factor) for the tunnel
application was assessed using RocLab© software and is summarized in Table 5.4.7, Figures
5.4.6, and 5.4.7):
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
12
4
3.5
Shear stress (MPa)
10
8
6
4
2
3
2.5
2
1.5
1
0.5
0
0
-0.5
0
0.5
1
-0.5
1.5
0
0.5
Hoek-Brown
1
1.5
2
2.5
3
3.5
Normal stress (MPa)
Minor principal stress (MPa)
Mohr-Coulomb
Hoek-Brown
Mohr-Coulomb
Figure 5.4.6. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 51 in the middle unit of the Asmari Formation.
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
30
Shear stress (MPa)
25
9
8
7
6
5
4
3
2
1
0
20
15
10
5
0
-1.5
-1
-0.5
0
0.5
1
1.5
2
-2
Hoek-Brown
-1
0
1
2
3
4
5
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.4.7. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 66 in the middle unit of the Asmari Formation.
5.4.1.3. Upper Unit (Upper Asmari Formation- As.3)
The lithology of the upper Asmari Formation comprise 80 m of medium to thinly bedded
limestone, dolomitic limestone and marly limestone. The karstification is highly developed
especially at the top of unit. The porosity values based on petrographical analysis is 2.7% to
5.4% indicating high porosity for this unit. According to the lugeon test results the
permeability is medium to high. The rock quality designation (RQD) is 50% to 70% that
imply fair quality rock mass.
The uniaxial compressive strength tests and field tests (Schmidt hammer test) shows UCS
values of 35 to 84 MPa.
The RMR values based on rock mass rating parameters in Table 3.3 were assessed as in
Table 5.4.8.
473
Table 5.4.8. Assessment of Rock Mass Rating for the Asmari Formation (Upper unit).
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition of discontinuities
Ground water
Adjustment for joint orientation
Value
35- 84
50% - 70%
0.2-0.6 , 0.6- 2m,
Rough to Smooth
Wet to Dripping
Very favorable
Rating
4- 7
13
10- 15
20- 25
4- 7
0
Total : 51– 67 (Fair to Good)
The Quality Index, Q calculated indirectly from the equation 3.10.
The Q values vary between 3.9 (Fair Quality) to 58.4 (Extremely Good Quality).
The geological strength index (GSI) based on two simple equations 3.11 and 3.12 which
introduced by Hoek and Brown (1997).
The GSI values vary between 46 and 62.
The rock mass strength with input data, UCS, GSI, mi, D for tunnel application was assessed
and are summarized in Table 5.4.9, Figure 5.4.8, and Figure 5.4.9:
Table 5.4.9. The rock mass strength in the Upper Asmari unit.
Hoek-Brown Classification
sigci
35 MPa
GSI
46
mi
8
D
0
mb
1.2
s
0.002
a
0.5
Failure Envelope Range
Application Tunnels
sig3max 1.3
MPa
Hoek-Brown Criterion
Unit Weight 0.03 MN/m3
Tunnel Depth
100 m
Mohr-Coulomb Fit
c
0.5 MPa
phi (ϕ) 43°
Rock Mass Parameters
sigt -0.07
MPa
sigc 1. 7
MPa
sigcm 5.02
MPa
Em 4699.3
MPa
Hoek-Brown Classification
sigci
84 MPa
GSI
62
mi
8
D
0
Hoek-Brown Criterion
mb
2.1
s
0.01
a
0.5
Failure Envelope Range
Application Tunnels
sig3max 1.4
Mpa
Hoek-Brown Criterion
Unit Weight 0.03 MN/m3
Tunnel Depth
100 m
Mohr-Coulomb Fit
c
1.6 MPa
phi (ϕ)
52°
Rock Mass Parameters
sigt
-0.6
MPa
sigc
10.07
MPa
sigcm 17.5
MPa
Em 18286.9
MPa
471
Normal Stress vs. Shear Stress
Principal Stresses
-0.5
3.5
3
Shear stress (MPa)
Major principal stress (MPa)
10
9
8
7
6
5
4
3
2
1
0
2.5
2
1.5
1
0.5
0
0
0.5
1
-0.5
1.5
0
0.5
1
Hoek-Brown
1.5
2
2.5
3
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.4.8. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 46 in the upper unit of the Asmari Formation.
Normal Stress vs. Shear Stress
Principal Stresses
8
7
Shear stress (MPa)
Major principal stress (MPa)
25
20
15
10
5
6
5
4
3
2
1
0
0
-1
-0.5
0
0.5
1
-1
1.5
Hoek-Brown
0
1
2
3
4
5
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.4.9. Relationship between major and minor principal stresses also normal and shear stresses for
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 62 in the upper unit of the Asmari Formation.
Taking all of the geological strength index values (GSI) of the three rock units of the
Asmari Formation into account, the rock mass strength of the Marun dam project can be
presented in Figure 5.4.10.
Figure 5.4.10 has been used to estimate the GSI value from field observations of blockiness
and discontinuity surface conditions.
The assessment of the strength and other engineering properties of the rock mass of the
Asmari Formation at the Marun dam site resulted in Figures 5.4.10 and 5.4.11. The rock mass
quality variations are from Blocky- Well Interlocked and Good (BG) to Very BlockyInterlocked and Fair (VB/F).
475
Figure 5.4.10. General Geological Strength Index (GSI) chart, for jointed rock
masses (Hoek and Brown 1997, Hoek and Karzulovic, 2001). The shaded area
is indicative of distribution of geological strength index of various rock mass
units of the Asmari Formation at the Marun dam.
476
ASMARI FORMATION
370.0 m
Figure 5.4.11. The lithological units and engineering rock mass characterization
of the Asmari Formation at the Marun dam.
477
5.5. Engineering Geological Characteristics of the Seymareh Dam and Power plant Project
(Engineering Rock Mass Classification of the Asmari Formation)
5.5.1. Lower Unite (Lower Asmari Formation- As.1)
This unit lithologically comprise 188 m medium bedded, fossiliferous dark grey marly
limestone and microcrystalline limestone. Only 12 m of this unit outcrops in the area around
the anticline axis. The porosity varies between 1.4% to 5.2% that indicates high porosity
index.
The rock quality designation (RQD) is about 80%, which indicates good quality rock mass.
The permeability values vary from impermeable to medium permeability for this unit. The
uniaxial compressive strength (UCS), based on Schmidt hammer field tests and laboratory
tests about 95 MPa. The general specifications of the major discontinuity sets in the area are
listed in the Table 5.5.1 below.
Table 5.5.1. Major discontinuity sets and their specifications.
Discontinuity Set
Set 1
Set 2
Set 3
Bedding
Dip Direction (°)
170- 175
270-275
120-130
010- 020
Dip (°)
65-75
80-90
70-80
25-35
Spacing
0.55 m
0.65 m
1.4 m
0.35- 3m
Discon. surface
Rough-wavy
Rough-wavy
Rough-wavy
Rough-wavy
Opening
2-20mm
2-20mm
2-20mm
<2mm
Filling
clay, calcite
clay, calcite
clay, calcite
none
Length
3-10m
3-10m
3-10m
>10 m
The RMR value for the lower unit of the Asmari Formation (As.1), based on rock mass rating
parameters from Table 3.3 can be assessed as in Table 5.5.2.
Table 5.5.2. Assessment of Rock Mass Rating for the Lower Asmari unit (As.1).
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition discontinuities
Ground water
Adjustment for joint orientation
Value
95
80%
0.55- 1 m
Rough to wavy
Wet to Dripping
favourable
Total : 56 – 61 ( Fair to Good )
Rating
7
17
10- 15
20
7
-5
The rock tunneling quality index (Q) can be indirectly determined by two emprical equations
(3.2.5, 3.2.6) introduced by (Bieniawski, 1989) and (Rotelech, Preston, 1978).
Based on equation 3.10, the Q values were determined as 9.1 (Fair Quality) and 21.1 (Good
Quality).
The Geological Strength Index (GSI) according to equations 3.11 and 3.12 (Hoek and Brown,
1997) was estimated to be between 51 and 56.
The rock mass strength with input data, UCS, GSI, mi, D for general applications, was
assessed using RocLab© software and Table 5.5.3, Figures 5.5.1 and 5.5.2 are the summary
of the results.
478
Table 5.5.3. The rock mass strength in the Lower Asmari unit.
Hoek-Brown Classification
sigci
95 MPa
GSI
51
mi
8
D
0
Hoek-Brown Criterion
mb
1.4
s
0.004
a
0.5
Failure Envelope Range
Hoek-Brown Classification
sigci
95 MPa
GSI
56
mi
8
D
0
Hoek-Brown Criterion
mb
1.7
s
0.01
a
0.5
Failure Envelope Range
Application General
sig3max 23.8
MPa
Mohr-Coulomb Fit
c
4.5 MPa
phi (ϕ) 28.9°
Rock Mass Parameters
sigt
-0.3
MPa
sigc
6.1 MPa
sigcm 15.3 MPa
Em 10324.3 MPa
Application General
sig3max 23.8
MPa
Mohr-Coulomb Fit
c
4.9 MPa
phi (ϕ) 30.4°
Rock Mass Parameters
sigt
-0.4 MPa
sigc
8.1 MPa
sigcm
17.1 MPa
Em
13767.7 MPa
Normal Stress vs. Shear Stress
Principal Stresses
-5
30
25
Shear stress (MPa)
Major principal stress (MPa)
90
80
70
60
50
40
30
20
10
0
20
15
10
5
0
0
5
10
15
20
-10
25
0
Hoek-Brown
10
20
30
40
50
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.5.1. Relationship between the major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 51 in the lower Asmari Formation.
Normal Stress vs. Shear Stress
Principal Stresses
-5
35
30
Shear stress (MPa)
Major principal stress (MPa)
100
90
80
70
60
50
40
30
20
10
0
25
20
15
10
5
0
0
5
10
15
20
25
0
10
20
30
40
50
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
-10
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.5.2. Relationship between the major and minor principal stresses as well as the normal and shear
stresses for the Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 56 in the lower Asmari Formation.
479
5.5.2. Middle Unit (Middle Asmari Formation- As.2)
Diversion Tunnel
The river diversion system at the Seymareh dam consists of a rock fill cofferdam 322 m
long and 24 m high with two diversion tunnels, 473 m, 395 m long and 10.5, 8.2 m in
diameter respectively. The downstream cofferdam is also a rock fill structure, 120 m long and
11 m high. The diversion tunnels are constructed in the right flank and pass through the
middle and upper Asmari units. The topographic gradient at the inlet is about 30° but the
outlet constitutes an escarpment with gradient nearly 80° (Figures 5.5.3 and 5.5.4).
Elevation (m)
LEGEND:
U.Asmari (As.3);
Medium to thin bedded
microcrystalline
limestone and
marlylimestone
M.Asmari (As.2);
Massive to thickly
bedded crystalline
limestone, dolomite and
marly limestone
L. Asmari (As.1);
Medium bedded
limestone,
marlylimestone
0
50
100
150
m
Figure 5.5.3. Engineering geological section along the diversion tunnels. These tunnels pass through the
middle and upper Asmari Formation limestone and are 473 m and 395 m long with 10.5 m and 8.2 m diameter
respectively (after MG co., 2009).
The Middle unit of the Asmari Formation lithologically comprises 238 m light to dark
grey massive to thickly bedded fossiliferous/ crystalline limestone, dolomitic limestone and
marly limestone. Except for the first part of the diversion tunnels, all dam structures are
founded in this unit. Karst features are observed throughout the unit. The porosity value
for the lower part is 7.5% that implies high porosity and gradually decreases in the upper part
to 0.95%. The permeability, based on lugeon test results, indicates low to high values.
The uniaxial compressive strength (UCS) and rock quality designation (RQD) indicate
strengths of 70-100 MPa and 75%- 95% (good quality) respectively.
The RMR value for the middle unit of the Asmari Formation (As.2), based on rock mass
rating parameters from Table 3.3 can be assessed as in Table 5.5.4.
481
Table 5.5.4. Assessment of Rock Mass Rating for the Middle Asmari unit (As.2).
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition discontinuities
Ground water
Adjustment for joint orientation
Value
70- 100
75%- 95%
0.55- >3 m
Rough to wavy
Wet to Dripping
favourable
Total : 56 – 74 ( Fair to Good )
Rating
7-12
17-20
10- 20
20
7
-5
Diversion Tunnels
1
2
D/S. Cofferdam
Figure 5.5.4. Downstream view of the Seymareh dam and some accessory structures such as
diversion tunnels, spillway and down stream cofferdam. Some major joint sets and faults with
small displacement at right bank can be observed.
Based on Table 3.4 the guidelines for excavation and support of a 10.5 m span rock tunnel for
the above RMR values are shown in Table 5.5.5.
Table 5.5.5. Rock support types for good and fair rock mass in the diversion tunnel.
Rock mass
class
Excavation
II – Good rock
Full face, 1- 1.5m advance.
Complete support 20m from face
III – Fair rock
Top heading and bench, 1.5-3 m
advance in top heading.
Commence support after each
blast. Complete support 10 m
from face
Rock bolts (20 mm diameter,
fully grouted)
Locally, bolts in crown 3.5- 4 m
long, spaced 2.5m with
occasional wire mesh
systematic bolts in crown 3.5- 4
long, spaced 2.5 m in crown and
walls with wire mesh in crown.
484
Shotcrete
Steel
sets
20 mm in crown
where required
Non
20 mm in crown
where required
Non
The Stand up Time for the diversion tunnel with a 10.5 m diameter based on the Bieniawski
stand up time graph is 0.5×104 hours (208 days) for good quality rock and 2×102 hours (8.3
days) for fair quality rock.
The Rock Tunnelling Quality Index, Q (Barton, 1974) with values from Table 3.1.11 can be
determined based on equation 3.4.
In addition the Quality index (Q) can indirectly be determined by two experimental equations
3.9 and 3.10.
From these equations the Q-values vary between 9.1 (Fair Quality) and 191.4 (Extremely
Good Quality).
The Geological Strength Index (GSI) was calculated according to equations 3.11 and 3.12
(Hoek and Brown, 1997) and the values obtained vary between 51 and 69.
The rock mass strength with input data, UCS, GSI, mi, D (disturbance factor) and tunnel
depth was assessed using RocLab© software and Table 5.5.6, Figures 5.5.5 and 5.5.6
summarize the results:
Table 5.5.6. The rock mass strength in the Middle Asmari unit.
Hoek-Brown Classification
sigci
70 MPa
GSI
51
mi
8
D
0
Hoek-Brown Criterion
mb
1.4
s
0.004
a
0.5
Failure Envelope Range
Application Tunnels
sig3max
1.3 MPa
Unit Weight 0.03 MN/m3
Tunnel Depth
100 m
Mohr-Coulomb Fit
c
0.8 MPa
phi (ϕ) 49.2°
Rock Mass Parameters
sigt
-0.2
MPa
sigc
4.5
MPa
sigcm
11.2
MPa
Em 8862.4 MPa
Hoek-Brown Classification
sigci
100 MPa
GSI
69
mi
8
D
0
Hoek-Brown Criterion
mb
2.6
s
0.03
a
0.53
Failure Envelope Range
Application Tunnels
sig3max 1.4 MPa
Unit Weight 0.03 MN/m3
Tunnel Depth
100 m
Mohr-Coulomb Fit
c
2.8 MPa
phi (ϕ) 53.2°
Rock Mass Parameters
sigt
-1.2
MPa
sigc
17.8
MPa
sigcm 25.2
MPa
Em 29853.8
MPa
482
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
12
4
3.5
Shear stress (MPa)
10
8
6
4
2
3
2.5
2
1.5
1
0.5
0
0
-0.4
-0.2
0
0.2
0.4
0.6
-0.5
0.8
0
0.5
Hoek-Brown
1
1.5
2
2.5
Normal stress (MPa)
Minor principal stress (MPa)
Mohr-Coulomb
Hoek-Brown
Mohr-Coulomb
Figure 5.5.5. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 51 in the middle unit of the Asmari Formation.
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
30
Shear stress (MPa)
25
9
8
7
6
5
4
3
2
1
0
20
15
10
5
0
-1.5
-1
-0.5
0
0.5
-2
1
Hoek-Brown
-1
0
1
2
3
4
Normal stress (MPa)
Minor principal stress (MPa)
Mohr-Coulomb
Hoek-Brown
Mohr-Coulomb
Figure 5.5.6. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 69 in the middle unit of the Asmari Formation.
5.5.3. Upper Unit (Upper Asmari Formation- As.3)
The As.3 unit constitutes the upper part of the Ravandi Anticline and lithologically
comprise 150 m grey to dark grey microcrystalline limestone, bioclastic limestone and marly
limestone, karstified and medium to thin bedded.
The porosity values are between 0.75% to 4.4% indicating medium to high porosity index.
Permeability is high to very high. The UCS and RQD values, based on laboratory tests are
60- 100 MPa and 65%- 94% (fair to good quality) respectively.
The RMR value for the upper unit of the Asmari Formation (As.3) based on rock mass rating
parameters from Table 3.3 is assessed in Table 5.5.7.
483
Table 5.5.7. Assessment of Rock Mass Rating for the Upper Asmari unit (As.3).
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition discontinuities
Ground water
Adjustment for joint orientation
Value
60- 100
65%- 94%
0.55- >1 m
Rough to wavy
Wet to Dripping
favourable
Total : 52 – 69 ( Fair to Good )
Rating
7-12
13-20
10- 15
20
7
-5
The Rock Tunneling Quality Index, Q was calculated indirectly using the equations 3.9 and
3.10 and the results are between 4.6 (Fair Quality) and 82 (Very Good Quality).
The Geological Strength Index (GSI) was calculated according to the empirical equation 3.11
and 3.12 and the values vary between 47 and 64.
The rock mass strength with input data, UCS, GSI, mi, D (disturbance factor) and tunnel
depth was assessed using RocLab© software and Table 5.5.8, Figures 5.5.7 and 5.5.8 are the
summary of the results:
Table 5.5.8. The rock mass strength in the Upper Asmari unit
Hoek-Brown Classification
sigci
60 MPa
GSI
47
mi
8
D
0
Hoek-Brown Criterion
mb
1.2
s
0.003
a
0.5
Failure Envelope Range
Application Tunnels
sig3max 1.3
MPa
Unit Weight 0.03 MN/m3
Tunnel Depth
100 m
Mohr-Coulomb Fit
c
0.7 MPa
phi (ϕ) 47°
Rock Mass Parameters
sigt -0.1
MPa
sigc 3.03
MPa
sigcm 8.8
MPa
Em 6517.4
MPa
Hoek-Brown Classification
sigci
100 MPa
GSI
64
mi
8
D
0
Hoek-Brown Criterion
mb
2.2
s
0.02
a
0.5
Failure Envelope Range
Application Tunnels
sig3max 1.4
MPa
Unit Weight 0.03 MN/m3
Tunnel Depth
100 m
Mohr-Coulomb Fit
c
2.1 MPa
phi (ϕ) 53°
Rock Mass Parameters
sigt
-0.8
MPa
sigc
13.4
MPa
sigcm 21.9
MPa
Em 22387.2 MPa
481
Normal Stress vs. Shear Stress
Principal Stresses
-0.2
3
2.5
Shear stress (MPa)
Major principal stress (MPa)
10
9
8
7
6
5
4
3
2
1
0
2
1.5
1
0.5
0
0
0.2
0.4
0.6
0.8
-0.5
0
0.5
Minor principal stress (MPa)
Hoek-Brown
1
1.5
2
Normal stress (MPa)
Mohr-Coulomb
Hoek-Brown
Mohr-Coulomb
Figure 5.5.7. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 47 in the upper unit of the Asmari Formation.
Normal Stress vs. Shear Stress
Principal Stresses
7
6
Shear stress (MPa)
Major principal stress (MPa)
25
20
15
10
5
5
4
3
2
1
0
0
-1
-0.5
0
0.5
-2
1
0
1
2
3
4
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
-1
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.5.8. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 64 in the upper unit of the Asmari Formation.
Structural Stability Control and Rock Support Arrangement elements were determined by
using the RocScience Software UNWEDGE©.
Three major and one accessory discontinuity planes (Table 5.5.1) control the shape and
dimensions of rock wedges in the diversion tunnel. The main joint sets are Js1, Js2 and Js4
(bedding planes).
The safety factor, volume, dimensions, geometry, wedge weight, wedge length, excavation
face area and sliding direction of all blocks are shown in Figure 5.5.9 and Table 5.5.9.
Wedge 8 is the only unstable block of 6.6 m3 with a factor of safety about 1.2. If wedge
sliding takes place, the direction of sliding will be toward 087° at angle of 61°. Other blocks
based on the Unwedge© program are relatively stable during excavations. After installation
of support elements (Table below) the safety factor of Wedge 8 increased to about 3.3.
485
A
B
C
D
Figure 5.5.9. Dimensions, geometry and structural specifications of wedges resulting from
intersection of major joint sets Js.1, Js.2 and bedding planes (Js.4) at 10.5 m diameter
diversion tunnel of the Seymareh dam. A- Perspective view, B- Side view of tunnel
showing potentially unstable wedges, C (2D view) and D (3D view) of rock support
arrangement of the Asmari Formation limestone in the fair quality rock.
Table 5.5.9. The rock wedge specifications in the diversion tunnel resulted by Js.1, Js.2 and Js.4
Floor wedge [1]
Factor of Safety: stable
Wedge Volume: 7.2 m3
Wedge Weight: 19.3 tonnes
Wedge z-Length: 3.5 m
Excavation Face Area: 13.7 m2
Lower Left wedge [3]
Factor of Safety: 22.3
Wedge Volume: 15.6 m3
Wedge Weight: 42.1 tonnes
Wedge z-Length: 9.2 m
Excavation Face Area: 24.2 m2
Sliding Direction (trend, plunge): 84°, 12°
Upper Left wedge [4]
Factor of Safety: stable
Wedge Volume: 0.0 m3
Wedge Weight: 0.0 tonnes
Wedge z-Length: 1 m
Excavation Face Area: 0.02 m2
Sliding Direction (trend, plunge): 170°, 70°
Lower Right wedge [5]
Factor of Safety: stable
Wedge Volume: 0.2 m3
Wedge Weight: 0.4 tonnes
Wedge z-Length: 7.6 m
Excavation Face Area: 4.94 m2
Sliding Direction (trend, plunge): 359°, 29°
Upper Right wedge [6]
Factor of Safety: 5.4
Wedge Volume: 9.3 m3
Wedge Weight: 25.2 tonnes
Wedge z-Length: 7 m
Excavation Face Area: 17.1 m2
Sliding Direction (trend, plunge): 275°, 80°
Upper Left wedge [8]
Factor of Safety: 1.2
Wedge Volume: 10 m3
Wedge Weight: 27.1 tonnes
Wedge z-Length: 9.4 m
Excavation Face Area: 18.6 m2
Sliding Direction (trend, plunge): 87°, 61°
486
The rock wedges information and their specifications resulting from the intersection of Js.1,
Js.3 and Js.4 (bedding planes) can be shown in Figure 5.5.10 and Table 5.5.10.
According to this data, the small rock wedge 8 in the upper right will be the only unstable
block with factor of safety 0 during the excavation process.
After installation of support elements, the factor of safety will be sufficient to continue the
excavation operation, and it should also be considered that Js.3 is an accessory discontinuity
that sporadically occurs in the tunnel rock mass.
In the other cases, such as the intersection of Js.2, Js.3, Js.4 and Js.1, Js.2, Js.3 there are not
any significant instability.
A
B
Figure 5.5.10. Dimensions, geometry and structural specifications of wedges formed by
intersecting major joint sets Js.1, Js.3 and bedding planes (Js.4) in the diversion tunnel. APerspective view, B- Top view of tunnel showing potentially unstable wedges.
Table 5.5.10. The rock wedge specifications in the diversion tunnel resulted by Js.1, Js.3 and Js.4.
Lower Right wedge [3]
Factor of Safety: stable
Wedge Volume: 18.2 m3
Wedge Weight: 49.1 tones
Wedge z-Length: 6.2 m
Excavation Face Area: 23.0 m2
Upper Right wedge [4]
Factor of Safety: 12.5
Wedge Volume: 0.1 m3
Wedge Weight: 0.3 tones
Wedge z-Length: 2 m
Excavation Face Area: 1 m2
Sliding Direction (trend, plunge): 170°, 70°
Lower Left wedge [5]
Factor of Safety: 64.4
Wedge Volume: 0.5 m3
Wedge Weight: 1.3 tones
Wedge z-Length: 1.4 m
Excavation Face Area: 2.6 m2
Sliding Direction (trend, plunge): 43°, 27°
Upper Left wedge [6]
Factor of Safety: 4
Wedge Volume: 15.8 m3
Wedge Weight: 42.7 tones
Wedge z-Length: 6.3 6 m
Excavation Face Area: 14.1 m2
Sliding Direction (trend, plunge): 125°, 75°
Roof wedge [8]
Factor of Safety: 0.0
Wedge Volume: 0.03 m3
Wedge Weight: 0.1 tones
Wedge z-Length: 1.9 m
Excavation Face Area: 0.5 m2
Sliding Direction (trend, plunge): 0°, 90°
A finite element mesh is shown in Figure 5.5.11, constructed to simulate the loading
conditions of normal and shear stress and their distribution on all rock wedges in the
diversion tunnel. Except for (Js.1, Js.2 and Js.4) other discontinuity sets have smaller
influence on the instability of the tunnel. These wedges are mainly considered to be more
stable than the cases of A-B because of their geometry (shape) and in situ stress conditions.
487
A
B
C
D
E
F
Figure 5.5.11. Finite element mesh of normal and shear stresses for all possible
wedges due to intersection of discontinuities in the diversion tunnel. The critical
wedges based on distribution of shear stress and the shape of the wedge is A-B (Js.1,
Js.2 and Js.4 or bedding planes).
The rock mass strength of the Seymareh Dam is presented in 5.5.12 based on all the GSI
values and engineering rock mass properties (Figure 5.5.13) of the three rock units of the
Asmari Formation.
The values of the GSI in Figure 5.5.12 were derived from field observations of the blockiness
and discontinuity surface conditions.
The rock mass quality variations are from Blocky- Well Interlocked and Good (BG) to Very
Blocky- Interlocked and Fair (VB/F).
488
Figure 5.5.12. General Geological Strength Index (GSI) chart, for jointed rock
masses (after Hoek and Brown, 1997, Hoek and Karzulovic, 2001). The
shaded area is indicative of the distribution of the geological strength index of
the various rock mass units of the Asmari Formation at the Seymareh dam.
489
ASMARI FORMATION
491
572.0 m
Figure 5.5.13. The lithological units and engineering rock mass characterization of the Asmari
Formation at the Seymareh dam.
Continue
5.6. Engineering Geological Characteristics of the Salman Farsi Dam and Power plant
Project (Engineering Rock Mass Classification of the Asmari Formation)
5.6.1. Middle Unit (Middle Asmari Formation- As.2)
Diversion Tunnel (middle unit)
Geological data for the diversion tunnel derived from boreholes and surface mapping
show that the tunnel is constructed in the middle part of the Asmari Formation. This unit
comprise homogeneous and thickly bedded crystalline limestone and dolomitic limestone.
The Asmari Formation along the diversion tunnel is in fair to excellent quality rock with
RQDs generally ranging between 60% to 100%. The major discontinuity sets are shown in
Table 5.6.1.
The RMR values based on rock mass rating parameters from Table 3.3, can be assessed as in
Table 5.6.2.
Table 5.6.1. Major discontinuity sets and their specifications.
Discontinuity
Set
Set 1
Set 2
Set 3
Bedding
Dip Direction (°)
Dip (°)
Spacing
Discon. surface
Opening
Filling
Length
131
115
280
019
81
85
77
55
1m
0.3 m
1- 1.5 m
0.1- 1.2m
rough
rough
smooth
Smooth to rough
closed
closed
closed
none
calcite
none
>5m
6m
>5m
>10m
Table 5.6.2. Assessment of Rock Mass Rating for the Asmari Formation (Middle unit).
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition discontinuities
Ground water
Adjustment for joint orientation
Value
60- 84
60% - 100%
0.5- 3m
Rough to Smooth
Wet to Dripping
Very unfavorable
Total : 50 – 67 ( Fair to Good )
Rating
7
13- 20
10- 20
25
7
-12
In addition, based on Table 3.4, the guidelines for the excavation and support of a 15 m span
tunnel for the relevant RMR values are shown in Table 5.6.3.
Table 5.6.3. Rock support types for the middle unit in the diversion tunnel.
Rock mass
class
II – Good rock
III – Fair rock
Excavation
Full face, 1- 1.5 m advance.
Complete support 20 m
from face
Top heading and bench 1.53 m advance in top heading.
Commence support 10 m
from face
Rock bolts (20 mm diameter,
fully grouted)
Locally, bolts in crown 4-5 m
long, spaced 2m with
occasional wire mesh
Systematic bolts 5-6m long,
spaced 2m in crown with wire
mesh, sides locally if needed
Shotcrete
Steel sets
50 mm in crown where
required
Non
2Χ40 mm in crown and
30 mm in sides
Non
The Stand up Time for the diversion tunnel with 15 m diameter is assessed based on the stand
up time graph (Bieniawski, 1989):
494
The Stand up Time for the diversion tunnel is 2×103 hours (83 days) for good quality rock
mass and immediate collapse for fair quality rock mass.
The Rock Tunneling Quality Index, Q can be determined indirectly by two emprical equations
3.9 and 3.10 and the values are between 58.4 (Very Good Quality) and 6.4 (Fair Quality).
Structural Stability Control and Rock Support Arrangement elements were determined by
using the RocScience Software UNWEDGE©.
Table 5.6.1 shows the major discontinuity sets which control the shape and dimensions of
wedges in the diversion tunnel.
A
B
C
D
Figure 5.6.1. Dimensions, geometry and structural specifications of wedges due to
intersecting major joint sets Js.1, Js.3 and bedding planes in the diversion tunnel at the
Salman Farsi dam. A- Perspective view, B- Side view of tunnel showing potentially
unstable wedges, C (2D view) and D (3D view) of rock support arrangement in the middle
Asmari limestone of fair quality rock mass.
492
The factor of safety, volume, dimensions, geometry and other specifications of all wedges
because of intersecting of Js.1, Js.3 and bedding planes are shown in Figure 5.6.1 and Table
5.6.4.
Table 5.6.4. The rock wedge specifications at the diversion tunnel resulting from joint sets Js.1, Js.3 and bedding
planes.
Floor wedge [1]
Factor of Safety: stable
Wedge Volume: 177.6 m3
Wedge Weight: 479.6 tones
Wedge z-Length: 15.0 m
Excavation Face Area: 54.4 m2
Sliding Mode: unconditionally stable wedge
Lower Left wedge [4]
Factor of Safety: 12
Wedge Volume: 19.8 m3
Wedge Weight: 53.6 tones
Wedge z-Length: 11.0 m
Excavation Face Area: 52.2 m2
Sliding Mode: wedge sliding on joint 1
Sliding Direction (trend, plunge): 131°, 81°
Lower Right wedge [5]
Factor of Safety: 17.0
Wedge Volume: 12.2 m3
Wedge Weight: 33 tones
Wedge z-Length: 9.7 m
Excavation Face Area: 38.2 m2
Sliding Mode: wedge sliding along line
of intersection of joints 3 and 4
Sliding Direction (trend, plunge): 353°, 52°
Roof wedge [8]
Factor of Safety: 1.7
Wedge Volume: 153.9 m3
Wedge Weight: 415.6 tones
Wedge z-Length: 15.0 m
Excavation Face Area: 53.1 m2
Sliding Mode: falling wedge
Sliding Direction (trend, plunge): 0°, 90°
The figure represents the approximately real possible sizes of wedges, which can occur in the
tunnel.
In Figure 5.6.1 it is evident that the roof wedges are potentially unstable and they need to be
stabilized. The stabilization will be achieved by the placement of 5-6 m long bolts of Ф 20
(diameter), with 2 m spacing and two 40 mm shotcrete layers in the crown. In the sidewalls,
one layer 30 mm shotcrete and rock bolting may be required.
The dimensions on the number, length and capacity of the rock bolts are made on-site by
geotechnical staff using equilibrium calculations according to the volume of the wedges
defined by the measured trace lengths. For those wedges, which involve sliding on one plane
or along the line of intersection of two planes, rock bolts are installed across these planes to
increase the sliding factor of safety of the wedge to 1.5. For wedges, which are free to fall
from the roof, a factor of safety of 2 is used. This factor is calculated as the ratio of the total
capacity of the bolts to the weight of wedge and is intended to account for uncertainties
associated with the bolt installation. Early recognition of the potential instability problems,
identification and visualization of the wedges which could be released and the installation of
support at each stage of excavation, before the wedge bases are fully exposed, resulted in a
very effective stabilization program.
The finite element mesh shown in Figure 5.6.2, was constructed to simulate the loading
conditions of normal and shear stress and their distribution on all block wedges in the
diversion tunnel. Except for Js.1, Js.2, and Js.4 other discontinuities sets have less influence
on the instability of the tunnel and produce small and narrow wedges (C-D, E-F). These
wedges can be considered to be more stable than the cases of A-B and G-H mainly because
of their geometry (shape) and in situ stress. In the cases of C-D and E-F collapsibility is
limited to small blocks. To prevent these instabilities light support elements can be used
effectively. More information related to these structures are shown in Figure 5.6.2.
493
B
A
′
C
D
E
F
Figure 5.6.2. Finite elements mesh of normal and shear stresses for all possible wedges
because of intersection of discontinuities in the diversion tunnel. Critical wedges are
based on the distribution of shear stress and the shapes of wedges in A-B and G-H. In
the other cases, the instabilities will be small and local.
A-B (Js.1, Js.2, Js.4), C-D (Js.1, Js.2, Js.3), E-F (Js.1, Js.2, Js.4), G-H (Js.2, Js.3, Js.4).
491
G
H
Figure 5.6.2. Continued
Figure 5.6.3. Pattern and arrangement of rock support elements in good quality rock of the
middle unit of the Asmari Formation. The support elements will be spot bolting and 30
mm shotcrete in the roof and in the sides if needed.
Rock support arrangement for the two types of rock mass in the diversion tunnel, can be
introduced based on Table 3.1.10 (Bieniawski, 1989) and revised based on a 15 m span for
the diversion tunnel in fair quality rock mass (Figure 5.6.2):
-Bolt length – 5.0m to 6.0m Ф20.0mm, in crown, and in sides if required
-Spacing – 2.0 m
-Shotcrete – 40.0mm primary and 40.0mm secondary in crown, and in sides
30.0mm if required
495
The support arrangement for good quality rock mass in the diversion tunnel can be
considered to be as follows (Figure 5.6.3):
-Bolt length – 4.0m to 5m Ф20.0mm, spot bolting in crown, and in sides if
required
-Spacing – 2.0 m
-Shotcrete – 30.0mm in crown and in sides, 30.0mm if required
The factor of safety for unstable roof wedges, after installation of the support elements is
considered to be about 1.7 for the two cases of good quality and fair quality rock mass.
The geological strength index (GSI) was calculated using equations 3.11 and 3.12 and the
values obtained are between 45 and 62.
The rock mass strength with input data, UCS, GSI, mi, D (disturbance factor) and tunnel
depth was assessed using RocLab© software. Table 5.6.5, Figures 5.6.4 and 5.6.5 are the
summary of the results:
Table 5.6.5. The rock mass strength in the Middle Asmari unit.
Hoek Brown Classification
sigci
84 MPa
GSI
62
mi
12
D
0
Hoek Brown Criterion
mb
3.1
s
0.01
a
0.5
Failure Envelope Range
Application Tunnels
sig3max 1.4
MPa
Unit Weight 0.03 MN/m3
Tunnel Depth
100 m
Mohr-Coulomb Fit
c
1.5 MPa
phi (ϕ) 55.9°
Rock Mass Parameters
sigt
-0.4
MPa
sigc
10.1
MPa
sigcm 20.8
MPa
Em 18286.9
Mpa
Hoek-Brown Classification
sigci
60 MPa
GSI
45
mi
12
D
0
Hoek-Brown Criterion
mb
1.7
s
0.002
a
0.5
Failure Envelope Range
Application Tunnels
sig3max 1.3
MPa
Unit Weight 0.03 MN/m3
Tunnel Depth
100 m
Mohr-Coulomb Fit
c
0.6 MPa
phi (ϕ) 50.2°
Rock Mass Parameters
sigt
-0.1
MPa
sigc
2.7
MPa
sigcm 10.2 MPa
Em 5808.7 Mpa
496
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
16
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Shear stress (MPa)
14
12
10
8
6
4
2
0
-0.5
0
0.5
1
-1
1.5
0
Hoek-Brown
1
2
3
4
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.6.4. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 45 in the middle unit of the Asmari Formation.
Normal Stress vs. Shear Stress
Principal Stresses
Major principal stress (MPa)
30
8
7
Shear stress (MPa)
25
20
15
10
5
6
5
4
3
2
1
0
0
-0.5
0
0.5
1
1.5
-1
0
Hoek-Brown
1
2
3
4
5
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.6.5. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 62 in the middle unit of the Asmari Formation.
5.6.2. Lower Unit (Lower Asmari Formation- As.1)
The lower unit comprises regularly bedded fined grained brown limestone and marls, thin
to very thinly bedded, with vug, channel and fracture porosity. The rock mass rating can be
assessed as in Table 5.6.6 for the discontinuity set specifications as in Table 5.6.1, and the
RMR parameters.
Table 5.6.6.Assessment of Rock Mass Rating for the Asmari Formation (Lower unit).
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition discontinuities
Ground water
Adjustment for joint orientation
Value
46- 65
37% - 50%
0.06- 0.6m
Rough to Smooth, weathered
Damp
Very unfavorable
Total : 25 – 40 (Weak )
497
Rating
4-7
8
8- 10
20
10
-25, -15
The Rock Tunneling Quality Index, Q can be calculated indirectly using equation 3.10
(Rotelech-Preston, 1978).
The Q values vary between 0.047 (Extremely Poor) to 0.6 (Very Poor).
The geological strength index (GSI) was calculated usining equations 3.11 and 3.12 and the
values obtained vary between 20 and 35.
The rock mass strength with input data, UCS, GSI, mi, D (disturbance factor) and tunnel
depth was assessed using RocLab© software. Table 5.6.7 and Figure 5.6.6 are summaries of
the results obtained.
Table 5.6.7. The rock mass strength in the Lower Asmari unit.
Hoek Brown Classification
sigci
46 MPa
GSI
20
mi
7
D
0
Hoek Brown Criterion
mb
0.4
s
0.0001
a
0.5
Failure Envelope Range
Hoek Brown Classification
sigci
65 MPa
GSI
35
mi
7
D
0
Hoek Brown Criterion
mb
0.7
s
0.001
a
0.5
Failure Envelope Range
Application General
sig3max 11.5 MPa
Application General
sig3max 16.3 MPa
Mohr-Coulomb Fit
c 1.1
MPa
phi (ϕ) 18.8°
Rock Mass Parameters
sigt -0.02 MPa
sigc
0.4 MPa
sigcm 3.1 MPa
Em 1206.1
MPa
Mohr-Coulomb Fit
c 2.2
MPa
phi (ϕ)
23.3°
Rock Mass Parameters
sigt
-0.1 MPa
sigc
1.6 MPa
sigcm 6.8 MPa
Em 3399.8 MPa
Normal Stress vs. Shear Stress
Principal Stresses
-5
14
12
Shear stress (MPa)
Major principal stress (MPa)
50
45
40
35
30
25
20
15
10
5
0
10
8
6
4
2
0
0
5
10
15
20
0
5
10
15
20
25
30
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
-5
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.6.6. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 35 in the lower unit of the Asmari Formation.
498
5.6.3. Upper Unite (Upper Asmari Formation- As.3)
The Upper Asmari unit comprises heterogenous alternating thinly bedded shelly
limestone, and marly limestone with marls, dolomitic limestone and siltstone, moderate to
weak strength, with vug and channel porosity.
Discontinuity set specifications in Table 5.6.1 and RMR factors lead to a rock mass rating
RMR calculated as shown in Table 5.6.8.
Table 5.6.8. Assessment of Rock Mass Rating for upper unit of the Asmari Formation.
1
2
3
4
5
6
Property
UCS (MPa)
RQD
Spacing of discontinuities
Condition discontinuities
Ground water
Adjustment for joint orientation
Value
39-46
58%
0.06- 0.6m
Rough to Smooth, weathered
Damp
Very unfavorable
Total : 25 – 42 (Weak to Fair)
Rating
4
13
8- 10
20
10
-25, -15
The Rock Quality Index, Q can be calculated indirectly by equation 3.10.
The Q values are estimated between 0.047 (Extremely Poor) and 0.84 (Very Poor).
The geological strength index (GSI) was calculated using equations 3.11 and 3.12 and the
values obtained vary between 20 and 37.
The rock mass strength with input data, UCS, GSI, mi, D (disturbance factor) for general
application was assessed using RocLab© software and Table 5.6.9, Figures 5.6.7 and 5.6.8
are a summary of the results obtained.
The rock mass strength of the Salman Farsi Dam is presented in Figure 5.6.9 based on all
the GSI values and engineering rock mass properties (Figure 5.6.10) of the three rock units of
the Asmari Formation.
The values of the GSI in Figure 5.6.9 were derived from field observations of the blockiness
and discontinuity surface conditions.
The GSI graph shows that the rock mass quality vary from Blocky-Well Interlocked and Good
(BG) to Blocky Disturbed/Seamy and Poor (BD/P).
Figure 5.6.10 shows the detail information regarding the engineering rock mass
characteristics resulting from the above calculations.
499
Table 5.6.9. The rock mass strength of the Upper Asmari unit.
Hoek Brown Classification
sigci
39 MPa
GSI
20
mi
7
D
0
Hoek Brown Criterion
mb
0.4
s
0.0001
a
0.5
Failure Envelope Range
Application General
sig3max 9.8
MPa
Mohr-Coulomb Fit
c
0.9
MPa
phi (ϕ) 18.8º
Rock Mass Parameters
sigt -0.01
MPa
sigc 0.3
MPa
sigcm
2.6 MPa
Em 1110.5
MPa
Hoek Brown Classification
sigci
46 MPa
GSI
37
mi
7
D
0
Hoek Brown Criterion
mb
0.7
s
0.001
a
0.5
Failure Envelope Range
Application General
sig3max 11.5 MPa
Mohr-Coulomb Fit
c
1.6
MPa
phi (ϕ) 23.8º
Rock Mass Parameters
sigt -0.06
MPa
sigc
1.3
MPa
sigcm 5.0
MPa
Em 3209.1
MPa
Normal Stress vs. Shear Stress
25
6
20
5
Shear stress (MPa)
Major principal stress (MPa)
Principal Stresses
15
10
5
4
3
2
1
0
0
-2
0
2
4
6
8
10
-5
12
0
Hoek-Brown
5
10
15
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.6.7. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 20 in the upper unit of the Asmari Formation.
Normal Stress vs. Shear Stress
35
12
30
10
Shear stress (MPa)
Major principal stress (MPa)
Principal Stresses
25
20
15
10
5
8
6
4
2
0
0
-2
0
2
4
6
8
10
12
-5
14
Hoek-Brown
0
5
10
15
20
Normal stress (MPa)
Minor principal stress (MPa)
Hoek-Brown
Mohr-Coulomb
Mohr-Coulomb
Figure 5.6.8. Relationship between major and minor principal stresses also normal and shear stresses for the
Hoek-Brown and equivalent Mohr-Coulomb criteria for GSI 37 in the upper unit of the Asmari Formation.
211
Figure 5.6.9. General Geological Strength Index (GSI) chart, for jointed rock
masses (Hoek and Brown 1997, Hoek and Karzulovic, 2001). The shaded area is
indicative of the distribution of the geological strength index of the various rock
mass units in the Asmari Formation at the Salman Farsi dam.
214
ASMARI FORMATION
650.0 m
Figure 5.6.10.The lithological units and engineering rock mass characterizations of the Asmari Formation
at the Salman Farsi dam project.
212
Chapter 6
The Engineering Geology of the Asmari Formation
and Implications on the Five Dam Sites
6.1. Introduction
The geomorphology is basically controlled by lithology, tectonic history, and
meteorological conditions. Therefore, the relatively high strength and rigidity of the Asmari
limestones on the one hand and the active tectonism of the region on the other hand explain
the steep gradients and occurrence in high peaks of the Asmari Formation limestones in the
Zagros region.
Carbonate rocks show elastic behaviour under normal stress. These rocks are stretched and
created anticline and syncline structures during the folding process. Likewise, the continuity
of these processes will result in reverse faulting, thrust faulting and imbricated structures as
well as subduction blocks over geologic time. Based on geological investigations in southwestern Iran, it is clear that the Zagros basin has undergone intensive folding, faulting and
subduction during its geological history (Nogole Sadat, 1985). It is believed that the
stretching process has resulted in break up of the outer layers in the southern flanks during
the extension stress/strain. Therefore, the highly curved southern flanks contain more
fractures than the low curved northern flanks and as such different engineering geological
characteristics can be expected on the two opposing flanks of the anticlines (Figure 6.1 and
6.2).
SCHEMATIC GEOLOGICAL SECTION OF ASMARI FORMATION
AT ZAGROS FOLDED BELT
SW
NE
Karun3
Karun4
Flow
Flow
(DS/US)
(DS/US)
(Fars group)
Seymareh
Marun
Salman Farsi
Gachsaran F. / Razak F.
(Fars group)
Gachsaran F. / Razak F.
Pabdeh F.
Asmari F.
Asmari F.
Gurpi F.
Legend:
Gachsaran Formation: (L. Miocene) Alternation of Salt, Anhydrite,
Gypsume, Marlstone, Marlylimestone, Sandstone, reddish brown
Pabdeh Formation: (Paleocene- L.Oligocene) Alternation
of Marly limestone, Marlstone and purplr Shale
Asmari Formation: (OligoMiocene), Alternation of light brownish
grey Limestone with marly Limestone and Marl, fossiliferous
Gurpi Formation: (Late Cretaeous), Marly limestone and
Marlstone
DS / US
River Flow
Down Stream / Up Stream
Dam body/
Cut off curtain
By: M. Koleini
Figure 6.1. Schematic geological cross section of Asmari Formation limestone at the Zagros folded belt. The
situation at the dam sites on each flank can be observed as well.
213
SW
B
1- Extensional Joints
2- Shear Joints
NE
1
2
A
B
A
Figure 6.2. A simple block diagram of Asmari formation limestone at the Zagros folded belt. Southern
flank clearly indicate much more gradient of strata between 70°- 90°, that the northern flank which has
dipping between 20° to 50° toward the northeast. Therefore, due to less curvature of strata, fewer
tectonic features can be expected.
A- Reverse and thrust faults due to compression in inner core and in two flanks of anticline.
B- Normal faulting due to extension in outer core of anticline.
1and 2 are extensional and shear joints respectively.
211
6.2. Permeability and Watertightness
Table 6.1 shows the average rock mass permeability of the Asmari Formation units,
measured in exploratory boreholes with lugeon tests. As can be seen the variation of this
parameter is caused by the existence of discontinuities with different lithological
characteristics. The permeability values indicate large variation in hydraulic conductivity
with depth and location. In addition to the hydrogeological anisotropy, this is one of the
important characteristics of the dam sites. Generally, in the Asmari Formation, to a depth of
100 m below surface, the hydraulic conductivity varies from very low to very high with the
majority of the results in the high range. Below this depth, the measurements indicate very
low to medium hydraulic conductivities except at Karun-4 and Salman Farsi which indicate
high permeability due to low values of RQD.
Table 6.1. The permeability conditions of various unit of the Asmari Formation at the dam localities.
Asmari unit
U.Asmari
Karun-3
M to VH
(20- 100) lugeon
M.Asmari
L.Asmari
M to VH
(10- 100) lugeon
Karun-4
Non to V.H
(0- 100) lugeon
M to V.H
(20- 100) lugeon
H to V.H
(30- 100) lugeon
Seymareh
H to V.H
(30- 74) lugeon
L to H
(4- 45) lugeon
Non to M
(1- 20) lugeon
Marun
M to H
(10- 30) lugeon
L to M
(2- 10) lugeon
Salman Farsi
Non to L
(1- 10) lugeon
L to V.H
(10- 100 ) lugeon
L to M
(3- 25) lugeon
L to V.H
(3- locally 100) lugeon
There is possibly a direct relationship between high coefficients of permeability values
and fractured zones. Some zones of high conductivity are probably caused by solution
enlargement of the fractures.
Generally, the upper Asmari Formation has relatively higher values of permeability than the
middle and lower parts, except at Salman Farsi where impermeable marlstones and marly
limestones are widespread. In general, impermeable layers such as marlstone, shale and
marly limestone play the main role to reduce the permeability values in each unit. The upper
Asmari unit (medium to thinly bedded) show higher influence of shear and extensional joints
due to tectonic compressional movements than the other units and therefore lower RQD
values can be expected (Figure 6.3).
RQD%
Min
Max
Upper Asmar (U)
Middle Asmari (M)
Lower Asmari (L)
Figure 6.3. Histogram of RQD values for the Asmari formation limestone, calculated for Karun-3 (K-3),
Karun-4 (K-4), Seymareh (Se), Marun (M), and Salman Farsi (Sa) dam sites.
215
SW
NE
Asmari Formation
Reservoir
Pabdeh Formation
Gachsaran Formation
A
SW
NE
Asmari Formation
Reservoir
Gachsaran Formation
Pabdeh Formation
B
Figure 6.4. The different geological condition of dam localities, (A) Seymareh, Marun, Salman Farsi in
the northern flank and (B) Karun-3, Karun-4 in the southern flank of the anticlines. The situation of the
dam body/cut-off curtain and reservoir on one hand and distribution of the Pabdeh, Asmari and
Gachsaran formations with various permeabilities on the other hand is of considerable matter in the
point of view of permeability and watertightness.
216
The permeability conditions of the Asmari Formation limestone clearly indicate a direct
relationship with RQD. It should be considered that the kind and thickness of fracture fillings
is also a very important factor leading to reduction in permeability values.
For example, joints with clay mineral infill are almost impermeable but are considered to be
discontinuities when calculating RQD.
The Asmari limestone ridges on either side of the dams are dissected by the subparallel
system of vertical and subvertical discontinuities (shear / extensional joints and faults),
running across the axis of the anticlines. Karstic features commonly developed along these
discontinuities and along steeply dipping planes can possibly provide a direct hydraulic
connection between the reservoir and the gorge downstream of the dams, i.e. there is the
possibility of substantial seepage from the reservoir bypassing the dam. Thus, the grout
curtains have to be placed in such a way to intersect these discontinuities.
The geological formations which form the reservoir rock bed from old to young generally
comprise the Khami Group, Ilam, Gurpi, Pabdeh, Asmari, Gachsaran, Aghajari and Bakhtiary
Formations respectively. In addition to the mentioned formations, the surficial materials such
as residual soil, slope wash, rock fall and river alluvium are also present in the reservoir
areas.
The distributions of geological formations in reservoir areas are not uniform, and they
constitute various areas of reservoir bedrock. Generally, the Gurpi and Pabdeh Formations
generally outcroup at the southern flank of the reservoir valley with the Gachsaran and
Aghajari Formations outcroupping on the northern flanks.
Watertightness of the reservoir areas depends on the occurrence of the two formations with
relatively high permeability mainly the Asmari and Gachsaran Formations.
The Asmari Formation is discussed in detail for each of the dam sites and has variable
permeability (non/low to very high).
The Gachsaran Formation comprises gypsum, anhydrite, salt and marl with occasional
thin beds of limestone. The rocks are generally of low strength with medium strength in the
limestone beds. The different lithological units vary in thickness. The marly parts usually
have low permeability or are impermeable while the other rock types are permeable with
several karst features present in the reservoir areas.
The karst development is believed to be shallow and laterally developed, but evaporites are
highly susceptible to karst development in depth (Xuepu, 1988).
This phenomenon can cause deep-seated reservoir leakage along karstic channels in gypsum,
although the gypsum layers are confined by impervious marl beds in some localities. This
situation needs careful re-examination in the next stage of investigation or construction
phases.
From the above results, it is concluded that seepage losses from the dam abutments and
reservoirs are expected and further studies should be carried out. In this regard, Figure 6.4
clearly indicates the various geological scenarios of foundation rocks relative to dam
body/cut-off curtains and the reservoirs, karstification, and watertightness. In case A
(northern flank sites) the dam foundations are on the Lower and Middle Asmari and the cutoff curtain is suspended in relatively permeable limestones of the Lower Asmari unit,
whereas in case B (southern flank sites) the Lower to Middle Asmari form the dam
foundation rocks and the cut-off curtain is locked in the impervious marls of the Pabdeh
Formation.
Case B is obviously more favourable than with regards to watertightness and possible deepseated leakage through the dam foundation rocks.
217
6.3. Slope Stability Analysis
6.3.1. Slope Mass Rating (SMR)
Based on the stereographic projection of the major joint sets (Figure 6.5) the critical
planes for planar and toppling failures as well as the joint critical intersections for wedge
failures were identified (Table 3.7, 3.8, 3.9). The F1, F2, F3 factors were determined in each
case according to the slope face dip direction and dip, and the F4 for natural slopes was used.
The SMR values (Table 6.2) in addition to the stereographic projection of the joint sets
clearly indicate a potential for planar failure (sliding direction) into the reservoir at
Seymareh, Marun and Salman Farsi, whereas at Karun-3 and Karun-4, the planar failures will
mainly occur towards the downstream area. The slope instability due to wedge and toppling
failures can be expected everywhere toward the reservoir and inside the dam valley.
Table 6.2. The SMR values for various units of the Asmari Formation rocks in the study area.
Dam site
Karun-3
Karun-4
Seymareh
Marun
Salman Farsi
Unit
RMR
RMRB
U.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
44-67
64-76
32-41
32-49
61-71
52-69
56-74
56-61
51-67
56-71
59-76
25-42
50-67
25-40
49-72
69-81
57-66
57-74
61-71
57-74
61-81
61-66
51-67
56-71
59-76
50-57
62-79
50-55
Slope Mass Rating (SMR)
Planar
20- 51
49- 60
29- 38
29- 42
33- 43
55- 71
49- 64
40- 47
-
Wedge
12- 36
24- 45
43- 52
43- 60
47- 57
Toppling
39- 62
50- 71
-
RB; 24- 48
LB; 65- 80
RB; 62- 79
LB; 40- 57
RB; 30- 55
LB; 10- 30
-
RB; 45-74
LB; 61- 90
40- 47
SMR values generally indicate that the Karun-3 and Karun-4 dam sites are unstable to
completely unstable, and the large planar and wedge failures can be expected towards the
gorge. It means that these two sites are subjected to more structural disturbances and dipping
strata.
Slope stability analysis (SMR) at the Seymareh, Marun, Salman Farsi dam sites indicates
unstable to partially stable rock slopes, especially in the reservoirs where big planar failures
can be expected. This is supposed by the historical rock slope failure (planar failure) at the
Seymareh dam where the Seymareh river bed was displaced about 1 000 m towards the
northeast (Koleini et al., 2010). Displacement and sliding of thousands of cubic metres of
rock and soil are the result of a large failure (Figures 4.5.1, 6.5 and 6.6).
A decrease in the shear strength of discontinuities after impoundment in addition to some
slope excavations during construction, such as dam abutments, tunnel headwalls and road
cuts can also reduce the SMR values according to the method of excavation (Table 3.8).
As a general rule, slopes should be designed to be no steeper than any steeply inclined sets of
discontinuities along which sliding may occur. Where a slope is undercut by steeply inclined
discontinuities or wedges formed by two or more sets of discontinuities, support must be
provided to prevent sliding. The overall inclination of any large cut will be no steeper than
the steepest natural slope of the same height in similar geological conditions. For example,
for slopes of 100 m or more in height, the overall gradient should be no steeper than 65° to
70° in the Asmari Formation or 45° in the Pabdeh Formation (Acres, 1982).
218
Karun-3, RB
Karun-3, LB
Karun-4, RB
Karun-4, LB
Seymareh
Marun
Salman Farsi
Figure 6.5. The stereographic projection of major discontinuity sets in the Asmari formation
limestones at the various dam locations. The slope stability based on intersections of major joint sets
and rock slope faces indicates various kinds of rock failures such as planar, wedge and toppling in the
area.
219
It should be considered that the SMR values are calculated only for natural slopes
(Romana, 1985). The active tectonics of the area, excavation of natural slopes and lowering
of discontinuity shear strength, resulting from reservoir impoundment can extensively
increase slope instabilities at all the dam sites. Knowledge of these factors enables a
preliminary assessment of the potential for continued or accelerated movement (or
reactivation) of the SMR and consequent damage to the projects over the extended time.
6.3.2. Falling Rock Hazard Index (FRHI)
Rockfall is another kind of rock slope instability at the area of research, especially at
Marun dam site (Koleini and Van Rooy, 2010). Among many natural hazards, rockfalls are
very frequent in mountainous areas. The term rockfall is usually used to describe small
phenomena from block falls of a few dm3 to thousands of m3. At the Marun dam site, rockfall
phenomena takes place almost every day in the downstream area. In the left flank power plant
and access roadways and in the right flank roadways, rockfalls are a hazard with falls from
cliffs of over 100 m high and dipping at 70°-90°. Observations show that the potential of a
large mass falling at this site, especially at the left flank where the power plant situated, is
high because of the dip direction of the bedding planes, joint system and the active tectonism
of the region. Both dam flanks were assessed according to the Falling Rock Hazard Index
(FRHI) classification method (Tables 3.10 and 3.11). Rockfall phenomena can also occur in
reservoirs where steep slopes are formed. These slopes are mostly on the Asmari Formation
(Figure 6.6).
The FRHI was developed based on work done earlier at the Oregon and Washington
Department of Transportation of United States (Singh, 2004). Many factors influence the
activation of fractured rock and weathered material to fall from a rock slope face (Table
3.10). Fractures, fissures, cracks, site vibrations and other external forces are related to rock
falling. Therefore, before undertaking an FRHI analysis, a stability analysis and survey of
rock structures need to be undertaken. In this research, an attempt was made to use this
method to determine the seriousness of falling rock hazard at the Marun dam site.
The FRHI at the Marun dam site assessed for minimum size of rock block of 10 - 20 kg.
Based on the relevant input data that are listed in Tables 3.10 and 3.11, the FRHI for the left
flank is moderate to high and for the right flank is a moderate risk (Table 6.3, 6.4 and Figure
6.8).
Table 6.3. Rock Fall Hazard Index score assessment at left flank.
Falling Rock Hazard Index
Face
height
Face
inclin.
Face
irreg.
Rock
condition
Spacing
discon.
Block
size
Volume
of RF
12
3
8
3-7
1-4
6- 7
7- 11
Exc.
method
4
Time
factor
Rockfall
freq.
8
8
Total score: 60 – 72
FRHI class: III - IV (Moderate to High Risk)
Table 6.4. Rock Fall Hazard Index score assessment at right flank.
Falling Rock Hazard Index
Face
height
Face
inclin.
Face
irreg.
12
9
3
Total score: 58 - 70
FRHI class: III (Moderate Risk)
Rock
condition
Spacing
discon.
Block
size
Volume
of RF
Exc.
method
Time
factor
Rockfall
freq.
3-7
1- 4
6-7
7-11
1
8
8
241
SW
NE
Asmari Formation
Pabdeh
Formation
Gachsaran Formation
A
SW
NE
Asmari Formation
Gachsaran Formation
Pabdeh Formation
B
Figure 6.6. The schematic block diagrams showing geological conditions of the Asmari formation
limestones as the main dam foundation rocks and dam localities in northern flank sites (A- Seymareh,
Marun, Salman Farsi) and in southern flank sites (B- Karun-3, Karun-4). They are typically indicating
various types of unstable slopes. In case A, planar and wedge failures toward the reservoir, and
wedged, toppling failures toward the gorge. In case B, wedge and toppling failures toward the
reservoir and gorge and planar failure toward the gorge will be expected.
244
Gachsaran Formation
Formation
Asmari Formation
Sliding surface
Gachsaran Formation
~ 1000 m
B
A
Asmari Formation
Figure 6.7. The typical block diagram and geological section of the Asmari and Gachsaran
formations in the Zagros folded belt and the possibility of land slide hazard after impoundment of
the reservoir. In general rock sliding adjacent to the dam locations toward the reservoir, will mainly
be planar (in Asmari limestones) and rotational to planar (in Gachsaran evaporites). As a result of
rock failure the Seymareh river bed was displaced about 1000 m toward the northeast during historic
times.
242
Left flank
160 m
A
Power house
Left flank
160 m
B
Power house
Right flank
160 m
C
Right flank
160 m
D
Figure 6.8. Rockfall hazard at Marun dam site in successive stages on the left flank (A, B) and right
flank (C, D). The power plant and access roadways are subjected to rock fall hazard every day.
243
6.3.3. Rock Slope Stabilization
Before the introduction of a suitable plan for rock slope protection, the short-term
instability of loose rock materials that can be removed and easily fall from the slope face
must be determined. Removal of loose rock materials can be done by scaling and there are
different ways to conduct rock slope scaling based on the specific project conditions. Hand
scaling with bars or rakes may be an adequate method for most short-term excavations where
the face height is less than three metres and only small fractured rocks are likely to fall
(Singh, 2004).
Long-term excavations, high slopes, and rock faces having large rocks and overhangs may
require heavier equipment, such as, hydraulic splitters, drag scaling, and light explosives
(trimming).
The identification of unstable ‘keyblocks’ will be required simultaneously with scaling of
the slope face at this stage. Release of keyblocks can sometimes precipitate rock falls of
significant size or in extreme cases large-scale slope failures.
There are different ways to protect a slope face from rock failure and rock fall events and
many companies manufacture such systems.
The general procedures to restraining rockfalls are listed below (Hoek, 2000):
 Berms are very effective means of catching rockfalls and are frequently used on
permanent slopes. However, berms can only be excavated from the top downwards
and they are of limited use in minimising the risk of rockfalls during construction.
 Rocksheds or Avalanche shelters are widely used on steep slopes above narrow
railways or roadways. An effective shelter requires a steeply sloping roof covering a
relatively narrow span. In the case of a wide multi-lane highway, it may not be
possible to design a rockshed structure with sufficient strength to withstand large
rockfalls. It is generally advisable to place a fill of gravel or soil on top of the
rockshed in order to act as both a retarder and a deflector for rockfalls.
 Rock traps work well in catching rockfalls provided that there is sufficient room at the
toe of the slope to accommodate these rock traps. In the case of very narrow roadways
at the toe of steep slopes, there may not be sufficient room to accommodate rock
traps. This restriction also applies to earth or rock fills and to gabion walls or massive
concrete walls.
 Catchment fences or Barrier fences are commonly used to absorb energy and are
designed for various capacities (Figure 6.9 and 6.10).
 Mesh draped, is commonly used for permanent slopes and is illustrated in Figure 6.11.
The mesh is draped over the rock face and attached at several locations along the
slope. The purpose of the mesh is not to stop rockfalls but to trap the falling rock
between the mesh and the rock face and so to reduce the horizontal velocity
component which causes the rock to bounce out onto the roadway below.
241
Column Retaining Rope
Grouted Anchor
Energy Absorbing Ring
Tensioned Cable
Column Foundation and Base Plate
Anchored/Foundation
Lateral view
Frontal view
Figure 6.9. Catchment fence or Barrier fence specifications and installation procedure (after Geobrugg
AG protection system, Switzerland, 2010).
B
A
C
Figure 6.10. Energy absorbing ring (A), when subjected to impact loading the ring
deforms plastically (B) and absorbs the energy of the boulder. (C) Impact sentinel
sensors check the status of rockfall protection systems and set off an alarm
(Geobrugg AG protection system- Switzerland, 2010).
The most common elements for stabilization of rock slopes are as follow (Hoek, 2000):
 Rock bolt; spot and systematic bolting (Figure 6.12)
 Wire mesh and chain link mesh
 Shotcrete
Fibre steel shotcrete can be used easily and effectively, where the slope face is not accessible
and dangerous for operation workers.
245
Figure 6.11. Rockfall control by free hanging mesh drape and its installation. It
is commonly used for permanent slopes. It can be used effectively at the right
flank of the Marun dam (after Fookes and Sweeney, 1976).
Shotcrete is the generic name for cement, sand and fine aggregate concretes which are
applied pneumatically and compacted dynamically under high velocity (Figure 6.13). Of the
many developments in shotcrete technology in recent years, two of the most significant were
the introduction of silica fume, used as a cementitious admixture, and steel fibre
reinforcement (Hoek, 2000).
Silica fume or micro silica is a by-product of the ferro silicon metal industry and is an
extremely fine pozzolan. Pozzolans are cementitious materials which react with the calcium
hydroxide produced during cement hydration. Silica fume, added in quantities of 8 to 13% by
weight of cement, can allow shotcrete to achieve compressive strengths which are double or
triple the value of plain shotcrete mixes. The result is an extremely strong, impermeable and
durable shotcrete (Hoek, 2000). Other benefits include reduced rebound, improved flexural
strength, improved bond with the rock mass and the ability to place layers of up to 200 mm
thick in a single pass because of the shotcrete's 'stickiness'. However, when using wet mix
shotcrete, this stickiness decreases the workability of the material and superplaticizers are
required to restore this workability (Hoek, 2000).
Steel fibre reinforced shotcrete was introduced in the 1970s and has since gained world-wide
acceptance as a replacement for traditional wire mesh reinforced plain shotcrete (Hoek, 2000)
(Figure 6.14). The main role that reinforcement plays in shotcrete is to impart ductility to an
otherwise brittle material. Steel fibres used in slab bending tests by Kompen (1989). The
fibres are glued together in bundles with a water soluble glue to facilitate handling and
homogeneous distribution of the fibres in the shotcrete (Hoek, 2000).
246
Locking nut
Rock bolt/ Ф 60 mm
Face plate
Breather tub
Grout injection tub
Figure 6.12. Systematic rock bolting (60 mm in diametre) of rock slope face at spillway- right flank
of Karun-4 dam (2007).
Shotcrete layer
(10- 15 cm)
Extensional
Joints
Figure 6.13. Rock slope failure after application of unreinforced shotcrete on marl units of the Asmari
Formation. The marls or such rocks need to be stablized by reinforced shotcrete due to ductility and
deformability of the rock mass. The vertical extensional joints and fractures due to gravity movement of the
rock mass can clearly be observed (Karun-3 dam site, entrance gate, 2007).
247
Figure 6.14. Steel fibre types available on the North American market (after Wood et al.,
1993). (Note: all dimensions are in mm).
6.4. Effect of Reservoir Impounding
The impounding of reservoirs may on occasion, destabilized the rock/soil masses forming
the dam and reservoir flanks and consequently cause landslides. Such landslides may vary
greatly in size and they may move very rapidly or very slowly. Landslides may move in
response to increased driving forces such as increased depth of saturation, or decreased
resisting forces such as loss of shear strength due to saturation along potential slip surfaces.
The stability of the reservoir rim depends on some parameters, such as reservoir water level,
the nature of formations which have most contact with reservoir water and dip into the
reservoir (Singh and Goel, 1999).
Landslides into the reservoir can cause severe damage such as partial or complete
blockage of the reservoir or by causing very large waves. Hypothetically at dam sites, the
critical case would be the occurrence of extremely large, rapid landslides of the rockfalldebris flow type. Such a rockfall-debris flow would travel at a high velocity and depending
on the volume of material involved, could create an enormous wave in the reservoir. If
generated close to the dam, they might destroy some structures and installations and in
addition, overtop the dams. It is however most unlikely that the dams would be seriously
damaged, but at Marun rockfill dam may be can cause serious impact and damage. In 1963 a
rapid landslide into the reservoir of the Vaijont arch dam in Italy caused a huge wave overtop
the dam. The dam suffered little damage but there was considerable damage downstream
(Hoek, 2000).
In view point of the above, it is necessary to assess the probability of landslide activity due
to impounding and the probability of damage to the project, should such landslides occur.
The instrumentation and monitoring of areas with high landslide potential during the design,
construction and operation phases will be helpful to recognise and forecast such phenomena
as well.
6.5. Engineering Classification of Rock Mass
The most common methods for evaluating the rock mass are engineering rock mass
classifications such as RQD, RMR, Q and GSI methods. The geomechanical parameters of a
248
rock mass are determined by using the results of rock mechanics lab tests (UCS) in addition
to Schmidt hammer field test and results of engineering rock mass classifications.
For this purpose the rock mass classification at each dam site was considered. The values of
RMR were calculated for each different rock unit, based on the data obtained from
exploratory boreholes, tunnels and results of laboratory tests, field tests and joints surveys.
Figures 6.15, 6.16 and 6.17 show frequency distribution of the RMR, UCS and GSI values
calculated for each dam site.
In this research the program RocLab© was used to estimate rock mass properties with
input data UCS, GSI, mi and D values, and the results introduced in Table 6.5.
The GSI values for the Asmari formation units were plotted on the basic GSI chart (Figure
6.18). They constitute various zones on the GSI chart according to their geological
characteristics. However the GSI zones fall close and relatively cover each other, but two
distinctive areas can be identified. The first zone is related to the Karun-3, Karun-4 Dams and
the other related to the Seymareh, Marun and Salman Farsi rock masses.
In the first case the rock mass is;
 Blocky- Very Well Interlocked and Good (B/G) to
 Blocky Disturbed and Fair (BD/F)
The GSI values are between 35 to 65.
In the second case the rock mass is:
 Blocky- Very Well Interlocked and Good (BG) to
 Very Blocky- Interlocked and Fair (VB/F)
The GSI values are between 45 to 70.
In case of Salman Farsi Dam it is however relatively well matched to the second case but
due to extensive development of marlstone, marly limestone with thin interbedded limestone
in the lower and upper units on one hand and extensive development of dissolution and
karstic features on the other hand a wide range of GSI values are present;
 Blocky- Very Well Interlocked and Good (BG) to
 Blocky Disturbed and Poor (BD/P)
The situation at each dam can be observed on the GSI chart in Figure 5.6.
In general four distinct areas can be distinguished on the GSI chart regarding the behaviour of
rock mass in Tunnelling Operations (Marinos and Hoek, 2005):
I.
Stable conditions; only at great depth possibillity of rock burst failures.
In very hard massive rock masses at great depths, spalling, slabbing and rockbursting
are the modes of failure that may develop, controlled by brittle fracture propagation in
the intact rock with only minor influence of the discontinuities.
II. Stability mainly controlled by structural failures.
Attention has to be concentrated on avoiding structural instabilities from wedges. This
makes structurally dependant instability more critical and generally demands heavier
rock bolting patterns and /or thicker shotcrete.
II/III. Stability controlled by structural failures or mild overstressing.
In the case of a more fractured limestone and marly limestone (eg. GSI values of 2540) the behaviour is controlled by sliding and rotation on discontinuity surfaces with
relatively little failure of the intact rock pieces (zone II/III). In this range of GSI
values the RQD values can be very low. This is normal, given the structure of the rock
249
mass, but some of the frictional behaviour of the unaltered pieces of the mass is
retained. Thus the control of stability can be effectively improved during excavation
of the tunnel by keeping the rock mass confined.
III. Stability controlled by stress dependent rock mass failure with significant squeezing at
depth.
RMR
Min
Max
Upper Asmar (U)
Middle Asmari (M)
Lower Asmari (L)
Figure 6.15. Histogram of RMR values for the Asmari formation limestone, calculated for Karun-3 (K-3),
Karun-4 (K-4), Seymareh (Se), Marun (M), and Salman Farsi (Sa) dam sites.
Ravelling from the face may occur in masses corresponding to the low areas of zone II/III
and in zone III.
In this case (poor quality rock mass such as marlstone and shale), due to either weathering or
shearing, blockiness may be almost completely lost and clayey sections with swelling
materials may be present.
Hoek and Karzulovic (2000) used the GSI and strength of rock masses and suggested a range
of GSI for different Excavation Methods. They proposed that the rock mass can be:
a) Dug up to GSI values of about 40 and a rock mass strength value of about 1 MPa.
b) Ripped up to GSI values of about 60 and a rock mass strength value of about 10 MPa.
c) Blasted when the GSI values are greater than 60 and rock mass strength value more
than 15 MPa.
221
UCS
MPa
Min
Max
Upper Asmar (U)
Middle Asmari (M)
Lower Asmari (L)
Figure 6.16. Histogram of UCS values for the Asmari formation limestone, calculated for Karun-3 (K-3),
Karun-4 (K-4), Seymareh (Se), Marun (M), and Salman Farsi (Sa) dam sites.
GSI
Min
Max
Upper Asmar (U)
Middle Asmari (M)
Lower Asmari (L)
Figure 6.17. Histogram of GSI values for the Asmari formation limestone, calculated for Karun-3 (K-3),
Karun-4 (K-4), Seymareh (Se), Marun (M), and Salman Farsi (Sa) dam sites.
224
Table 6.5. A summary of the engineering rock mass properties of the Asmari Formation at the different dam sites.
Dam site
Karun-3
Karun-4
Seymareh
Marun
SalmanFarsi
Unit
Porosity%
Permeability
U.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
0.75-13.8
1- 15.7
0.5- 5
1- 7
0.75- 15.2
0.75- 4.4
0.6- 7.5
1.4- 5.2
2.1- 5.4
1.4- 11
1.3- 14.9
1.5- 19.4
0.3- 8
1- 5.6
M- VH
M- VH
Non to V.H
M to V.H
H to V.H
H to V.H
L to H
Non to M
M to H
L to M
L to M
Non to L
L to V.H
L- VH (local)
UCS/MPa
15- 116
116- 138
39-48
39-116
48-100
60-100
70-100
95
35-84
35-95
60-84
39-46
43-84
46-75
RQD%
31-53
50-84
45-78
53-84
55-83
65-94
75-95
80
50-70
50-80
70-85
58
60-100
37- 50
RMR
44-67
64-76
32-41
42-49
61-71
52-69
56-74
56-61
51-67
56-71
59-76
25-42
50-67
25-40
Q
1.2-58.4
35.1-268.6
0.15-0.7
0.84-2.8
21-151
4.6- 82
9.1-191.4
9.1- 21.1
3.9-58.4
9.1-115.1
15.1-268.6
0.047-0.84
6.4- 58.4
0.047-0.6
222
GSI
39-62
59-71
27-36
37-44
56-66
47-64
51-69
51-56
46-62
51-66
60-71
20- 37
45- 62
20- 35
Mohr coulomb fit
C, MPa
Phi (°)
0.55-6.7
1.6-3.97
1.2-1.8
1.45-4.9
0.8-2.3
0.7-2.1
0.84-2.8
4.5-4.9
0.48-1.6
0.6-2.22
0.85-2.6
0.9- 1.6
0.64-1.5
1.1-2.2
24.4-32.1
57-57.4
21.9-24.6
24.9-26.9
47.8-53.1
47.3-53
49.2-53.2
28.9-30.4
43.2-52.1
44.5-52.9
48.8-52.5
18.8-23.8
50.3-55.9
18.8-23.3
Rock mass parameters
Sigt, MPa
-0.02 to -0.8
-0.6 to -1.7
-0.02 to -0.05
-0.04 to -0.2
-0.2 to -0.96
-0.14 to -0.83
-0.22 to -1.2
-0.3 to -0.43
-0.07 to -0.6
-0.1 to -0.9
-0.23 to -1.2
-0.13 to -0.06
-0.8 to - 0.4
-0.02 to- 0.07
Sigc, MPa
0.47- 13.9
11.7-27.4
0.54-1.23
1.07-4.9
4.08- 15
3.03-13.4
4.5- 17.8
6.1-8.1
1.7-10.1
2.23-14.3
4.6-16.7
0.3- 1.3
2.7-10.1
0.37- 1.6
Em, MPa
2056.1-19952.6
16788-33496.5
1661.6-3094.7
2954.8-7079.5
9786.4-25118.9
6517.4-22387.2
8862.4-29853.8
10324.3-13767.7
4699.3-18286.9
6266.6-24482.8
9751.6-30700.1
1110.54-3209.1
5808.66-18286.9
1206.1-3399.8
I
II
II/III
IV
Karun-3
Karun-4
Seymareh
Marun
Salman
Figure 6.18. Geological Strength Index (GSI) chart, for jointed rock mass (Hoek and Brown
1997, Hoek and Karzulovic, 2001, Marinos and Hoek, 2005). The shaded areas indicate the
distribution of geological strength index values of the various rock mass units of the Asmari
Formation.
223
6.6. Stability of Dams against Horizontal Sliding
6.6.1. DMR (Dam Mass Rating)
Bieniawski and Orr (1976) proposed the following adjustment factors for the effect of joint
orientation in horizontal stability (Table 6.6) based on experience and on consideration of
stress distributions in the foundation rock mass as well as on the assumption that in a dam
structure, both the arch and the gravity effects are present.
Table 6.6. Adjusting factor for dam stability after joints orientation (after Bieniawski and Orr, 1976)
Dam
Gravity
Dip (°)
Rating
VF
Very favourable
0- 10
0
F
Favourable
30- 60
-2
Fa
Fair
10- 30 DS
-7
U
Unfavourable
10- 30 US
-15
VU
Very unfavourable
60- 90
-25
Snell and Knigth (1991) approached the problem of dam stability systematically taking
account of all the forces and stresses acting on the dam. Based on their study, it appears that a
different set of adjusting factors must be applied. Table 6.7 shows these new tentative
adjusting factors according to the main discontinuity orientations. The numerical rating values
proposed originally by Bieniawski have been retained.
Table 6.7. Adjusting factors (RSTA) for the stability according to the joint orientation (after Romana, 2003)
Fill
VF
Very
favourable
Others
Gravity
10- 60 DS
10- 30 DS
30- 60 US
60- 90 A
Arch
RSTA
30- 60 DS
0
10- 30 DS
-2
Type of
Dam
F
FA
U
Favourable
Fair
Un favourable
0- 10 A
-
VU
Very
unfavourable
-
10- 30 US
30- 60 US
60- 90 A
-7
0- 10 A
-
10- 30 US
-15
0- 10 A
-25
DS. dip downstream, US. dip upstream, A. any dip
Gravity dams include CVC and RCC concrete dams
When the dip direction of the significant joint is not almost parallel to the downstreamupstream axis of the dam, the danger of sliding diminishes due to the geometrical difficulties
to slide. It is possible to take account of this effect by multiplying the rating of the adjusting
factor for dam stability RSTA, by a geometric correction factor (CF).
CF = (1- sin (αd – αj)) 2
(αd > αj)
(5.1)
2
CF = (1- sin (αj – αd))
(αj > αd)
(5.2)
Where αd is the upstream-downstream direction of the dam axis and αj is the dip direction of
the significant joint.
DMRSTA = RMRBD + CF × RSTA
(5.3)
Where RMRBD (basic dry RMR) is the addition of the RMR five parameters and RSTA is the
adjusting factor for dam stability (Table 5.9).
Actually there are no data allowing to establish a correlation between the value of DMRSTA
and the degree of safety of the dam against sliding. As a rule of thumb, it is suggested
(Romana, 2003) that if:
 DMRSTA > 60
No primary concern
221
 60 > DMRSTA > 30
 30 > DMRSTA
Concern
Serious concern
The above values can not be taken as numerical statements but only as danger signals for the
designer. Dam stability must always and in any case be checked by the designer taking into
account the distribution of pore water pressure across the dam foundation and of the
mobilized shear strength of the significant joints (Romana, 2003).
According to the DMRSTA values (Table 6.8) from the above calculations the stability of the
various dams against horizontal sliding can generally be classified into; No primary concern.
Table 6.8. DMR evaluation of dam foundation rocks at the five dam sites.
Dam site
Karun-3
Karun-4
Seymareh
Marun
Salman
Farsi
Unit
U.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
RMR
44-67
64-76
32-41
42-49
61-71
52-69
56-74
56-61
51-67
56-71
59-76
25-42
50-67
25-40
RMRBD
60- 80
70-89
62- 71
62- 79
72- 79
65- 82
69- 87
69- 74
62- 75
67- 79
70- 84
60- 62
70- 87
55- 60
αd
αj
RSTA
DMRSTA
78
270
230
-7
77
73
225
218
-7
67.4
77
197
30
-7
73
77
212
33
0
77
71
199
19
-2
69
Mean. Weighted
RMRBD
6.7. Underground Rock Support
The underground structures requiring rock support are the diversion tunnels, hydropower
tunnels and power chambers. The aim of the rock support is to ensure that the strength of the
rock surrounding the excavation is mobilized to the extent that the rock mass is self
supporting. In other words, this will be the primary form of support with no allowance or
contribution from linings placed for hydraulic purposes. The performance of any rock
support system during the lifetime of the excavation will be a function of the
load/deformation characteristics of the ground and lining. Further field and laboratory
investigations will be performed to accurately define these characteristics for detailed design.
The evaluation of tunnel support requirements has been done according to empirical
approaches by Bieniawski (1978) in which support requirements are determined by means of
a classification system.
In general rock bolting and shotcreting form the basis of the support system for the
tunnels. The level of application will depend on the quality of the rock mass. This is reflected
in three classes of support which are proposed for the tunnels. The differences in level of
support relate to variations in thickness of shotcrete, density and length of rock bolts,
application of steel wire mesh.
In this regard three rock mass ratings from the geomechanical classification of Bieniawski
(1984) were recognized.
1. Good quality rock mass (II)
Comprise massive to thickly bedded limestone, crystalline limestone and dolomitic
limestone
2. Fair quality rock mass (III)
Comprised marly limestone with thin interbedded limestone
225
3. Weak quality rock mass (IV)
Mainly comprise marlstone with thin interbedded limestone and shale.
These categories have support elements which have been discussed in detail in Chapter 3.
The three types of support elements can be summarized as follows:
II. Light Support
4 to 5 m rockbolt with 2.5 m to 2.5 m by 2.5 m to 2.5 m grids of bolts above the spring
line, fully grouted with locally wire mesh, 20 to 30 mm shotcrete in crown and in sides if
required.
III. Medium Support
5 to 6 m rockbolt with 2 m to 2 m by 2 m to 2 m grid of bolts in crown and sides, fully
grouted with wire mesh, 50 - 100 mm shotcrete in crown and 30 mm in sides.
IV. Heavy Support
5 to 6 m rock bolt with 1.5 m to 1.5 m by 1.5 m to 1.5 m grid of bolts in crown and sides,
fully grouted with wire mesh, 100- 150 mm shotcrete in crown and 100 mm in sides.
It is implicit in the above approach that the performance of the tunnel support systems should
be carefully checked and monitored during construction. This will allow a readjustment of
support levels, depending on the results.
6.8. Cuttability of Asmari Formation Limestone
The cuttability of rock is particularly important when using roadheader-boom type
tunnelling machines. According to Fowell and Johnson (1982), interpretation of borehole
information at the site-investigation stage for predicting roadheader cutting rates is facilitated
by the use of rock mass classifications.
Based on 20 field results, Fowell and Johnson (1982) derived a relationship between the RMR
values and the cutting rate (m3/h) for the heavyweight class of boom tunnelling machines.
The results are given in Figure 6.19. The authors reported that the only modification they
made in the use of the Geomechanics Classification was in the rating for orientation, since, for
excavation in general, an inverse relationship exists between support requirements and ease of
excavation. It can be concluded that the RMR system provide a remarkable consistent
relationship with the roadheader cutting rate.
The Cuttability rate of the Asmari formation limestones according to roadheader cutting rate
(boom tunnelling machine) of Fowell and Johnson (1982) experimental method is shown in
Table 6.9.
The cuttability rate for various rock mass type of the Asmari Formation can be categorized as
follows:
I.
Massive to thickly bedded Limestone
and Dolomitic limestone;
II. Medium to thinly bedded limestone, Marly limestone;
III. Marlstone and Shale;
226
15- 40 m3/h
60-100 m3/h
80- >160 m3/h
Cutting Rate m3/h
120
80
40
0
0
20
40
60
80
100
Rock Mass Rating (RMR)
Figure 6.19. Relationship between RMR and rock cutting rate. (after Fowell and
Johnson, 1982).
Table 6.9. The cuttability rates of the Asmari formation limestone based on Fowell and
Johnson (1982) experimental method.
Dam site
Karun-3
Karun-4
Seymareh
Marun
Salman Farsi
Unit
U. Asmari
L. Asmari
U. Asmari
M. Asmari
L. Asmari
U. Asmari
M. Asmari
L. Asmari
U. Asmari
M. Asmari
L. Asmari
U. Asmari
M. Asmari
L. Asmari
UCS/MPa
RQD%
15- 116
116- 138
39-48
39-116
48-100
60-100
70-100
95
35-84
35-95
60-84
39-46
43-84
46-75
31-53
50-84
45-78
53-84
55-83
65-94
75-95
80
50-70
50-80
70-85
58
60-100
37- 50
RMR
44-67
64-76
32-41
42-49
61-71
52-69
56-74
56-61
51-67
56-71
59-76
25-42
50-67
25-40
Cuttability
m3/h
79- 23
28- 16
135- 93
89- 64
34- 18
54- 20
44- 14
44- 34
58- 16
44- 18
37- 16
>160- 89
60- 23
>160- 97
6.9. Net Allowable Bearing Pressure Classification
The rock mass rating (RMR) of Bieniawski (1973) can be used to determine the net
allowable bearing pressure of a rock mass based on Table 6.10 (Singh, 1991 and Mehrotra,
1993). The information in Table 6.10 results from plate load tests at 60 construction sites for
spread foundations 6 m wide, and with a 12 mm settlement. Figure 6.20 indicates the precise
relationship between RMR values and net allowable bearing pressure carried out at the Indian
Institute of Technology Roorkee- India (Mehrotra, 1993).
227
Table 6.10. Net allowable bearing capacity according to RMR values (after Mehrotra, 1993).
I
Very Good
81- 100
440- 600
Rock Class
RMR
qa (t/m2)
II
Good
61- 80
280- 440
III
Fair
41- 60
135- 280
IV
Weak
21- 40
45- 135
V
Very Weak
0- 20
30- 45
Net Allowable Bearing Pressure (q a) MPa
3.0
2.5
2.0
1.5
1.0
0.5
0
15
20
25
30
35
40
45
50
55
60
Rock Mass Rating (RMR)
Figure 6.20. Relationship between net allowable bearing capacity and Rock Mass Rating in natural
moisture content (after Mehrotra, 1993).
In this case, the RMR values must be estimated for rock mass foundations to a depth equal
to the foundation width. If the upper parts of the foundation are in low quality rock mass, the
RMR values related to this part should be considered for foundation design, or this part
should be completely removed and filled by a suitable concrete design.
The net allowable bearing pressure values during seismic loading should be increased up to
about 50% according to the rock mass rheological behaviour (Mehrotra, 1993). The net
alloable bearing capacity of he Asmari Formation rock masses according to RMR values,
based on Mehrotra (1993) are classified in Table 6.11.
Table 6.11. The RMR values of the Asmari Formation limestone
Dam site
Karun-3
Karun-4
Marun
Seymareh
Salman Farsi
Unit
U.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
U.Asmari
M.Asmari
L.Asmari
RMR
44-67
64-76
32-41
32-49
61-71
51-67
56-71
59-76
52-69
56-74
56-61
25-42
50-67
25-40
228
Classification
Fair- Good
Good
Weak- Fair
Weak- Fair
Good
Fair- Good
Fair- Good
Fair- Good
Fair- Good
Fair- Good
Fair- Good
Weak- Fair
Fair- Good
Weak
6.10. Foundation Consideration
The entire area under the dams should be excavated to sound, fresh rock. The depth of the
planned foundation excavation has been determined by topographical considerations and is
well below the average depth of the weathered zone. As the dams will rest on the Asmari
Formation and considering this formation is weathered and crushed at surface, it is estimated
the depth of the materials to be removed will range from 1m to 10 m and on average 3-5 m.
The thickness of the alluvium to be removed from the river bed commonly ranges from 25 to
50 m. After the removal of weathered rock, the foundation will rest on sound rock. In addition
to the above mentioned, attention should also be paid to the dam abutments. In accordance
with exploratory adits and also the drilling investigation borehole data, there are some low
strength beds which have been eroded previously and then filled by secondary materials.
These materials should be removed from these locations. Filling materials along the faults
(brecciated zones and gouge materials) at foundation rocks should be replaced by suitable
concrete aggregate.
Dental excavation (so rough) of shear zones and weathered rocks should also be
performed. Such areas must be backfilled with concrete as necessary. Detached block of rocks
should be removed or rock bolted and or grouted. Rock overhangs must be trimmed and a
regular surface formed. The side walls of the foundation excavation should be cut taking slope
stability analysis into consideration preferably no more than natural gradient of the rock
slopes. In some areas, due to the presence of unstable rock blocks and wedges, pattern bolting
will be required, although local blocks or zones may require support in the form of rock bolts,
shotcrete or steel wire mesh. The occasional use of high tensile strength rock anchors in some
of the higher cut slopes should be considered.
6.10.1. Grouting
6.10.1.1. Consolidation Grouting
Consolidation grouting should be performed over the whole area of the dam foundation.
The consolidation holes should be drilled on a 3 m by 3 m grid pattern and should extend to a
depth of 10 m below the foundation. The orientation of the holes will be such that they
intersect the majority of discontinuities.
6.10.1.2. Curtain Grouting
Grout curtains are critical components of the dams constructed on slightly karstic bedrock
foundations. In this geological environment such as the Asmari formation limestone, grout
curtains are more extensive and require much higher volumes of cement than is normally the
case in other rock types (Acres, 1982).
The grout curtain should be extended to over 100 to 150 m below the base of the dam
foundation and over 200 m into each abutment (depending on karst development). A multiline
curtain, comprising 2 to 3 rows of holes, should be installed in the medium to high
permeability limestone in each abutment and beneath the dams. High grout takes can be
anticipated in this part of the grout curtain. The grouting will be performed mostly from
tunnel galleries and designed according to the size of drilling equipment. Grout holes will be
approximately 50 mm in diameter and have average spacings of 3 m, although spacings as
low as 1.5 m can be expected at some localities. The holes will be oriented such that they
intersect the maximum number of bed rock discontinuities.
229
6.10.2. Treatment of arge Caverns
All large cavities along the grout curtain alignment or close to the grout curtain will have
to be plugged with concrete, and the plug structures have to be connected to the curtain. An
acceptable uniform model for treatment of large karst voids does not exist.
Total filling of huge caverns with concrete should be avoided due to economical reasons.
Narrow parts in the rock mass (karst channels) have to be explored by dental investigations
for determining the best way for plugging (JV. Stucky/Electrowatt, 1992).
The general guidelines for the plugging technology above the water table are:
1.
2.
3.
4.
5.
6.
7.
Provision of access adits and shaft excavations from the main grouting galleries up to
the karst channels and cavities.
3D geological and speleological mapping for the purpose of treatment decisions.
Drilling into inaccessible (small diameter) karst voids, including geophysical
investigations.
Preparation of rock materials such as pebbles and boulders for partly filling of
accessible caves
Preparation of concrete pumps for concrete injection.
Preparation for rock bolt installation.
Provision of contact grouting after plugging operations.
The technology for large karst cavity treatment below the water table, however, without
using any back pressure (mostly from the lowermost galleries) needs large diameter drill rigs,
with preventers, operating from the grouting galleries. This is supposed to be a pure filling
process, without the use of packers.
Previous exact mapping with the provision of contours of every large cavity has to be
provided using small diameter rotary drilling and selected geophysical investigation methods
(JV. Stucky/Electrowatt, 1992).
6.11. Construction Materials
6.11.1. Granular Materials
Test pits have proven large amounts of very weakly cemented granular material in some
areas around the dam sites such as main and seasonal river bed alluvium. The test pits show
mostly stratified gravel and sandy gravel with minor amounts of silt and occasional cobbles
and boulders. Particles are rounded to subrounded and mostly composed of limestone. Most
particles have surface discoloration and in some cases alteration extends up to 1 mm into the
rock surface.
Sodium sulphate soundness tests indicate less than 10% losses after five cycles for materials
in some of the areas investigated and between 10% and 40% in some other areas. The specific
gravity ranges from 2.6 to 2.7. Fine material passing the No. 200 mesh (0.074 mm) varies
from 1% to 85% and gravel size from 0% to 95%.
6.11.2. Excavated Rocks
The use of excavated rocks or rocks from quarries is assumed to be the main source for
concrete aggregate. Assessment of suitability was based only on visual examination of rock
cores and excavated rock from adits, service record of similar rock at other structures,
petrographic examination and laboratory analysis such as alkali aggregate reaction (AAR).
231
According to the lithological columns shown in Figure 5.4, each unit which contained
higher percentages of interbedded marlstone, shale, marly limestones and dolomitic limestone
should be rejected for the concrete aggregates. These rock particles are often elongated with
sharp edges in addition to a platy shape and have a high potential for deterioration due to low
strength. In this regard it refers to the upper Asmari in Karun-3, lower Asmari in Salman Farsi
and Seymareh dam sites due to a high concentration of argillaceous mineral content.
The dolomitization of limestones can be observed in all dam foundation rocks. This
phenomenon varies from slightly to intensive dolomitization. For example the middle Asmari
unit at Seymareh and Salman Farsi dam sites are relatively influenced by high dolomitization
but at the other sites dolomitization is only observed locally.
It is generally believed that alkali-carbonate reaction occurs between certain argillaceous
dolomitic limestones and the alkaline pore solution in the concrete.
Alkali-aggregate reaction is a chemical reaction between certain types of aggregates and
hydroxyl ions (OH-) associated with alkalis in the cement. Usually, the alkali comes from the
Portland cement but it may also come from other ingredients in the concrete or from the
environment. Under some conditions, the reaction may result in expansion and cracking of the
concrete. Concrete deterioration caused by alkali-aggregate reaction is generally slow, but
progressive (Shrimer, 2005).
Cracking due to alkali-aggregate reaction generally becomes visible when concrete is 5 to 10
years old. The cracks facilitate the entry of de-icing salt solutions that may cause corrosion of
the reinforcing steel, thereby accelerating deterioration and weakening a structure (Shrimer,
2005).
Finally, the suitability of the Asmari limestone for use as concrete aggregate must be
confirmed by further laboratory testing. Samples should be tested for gradation, absorption,
specific gravity, sulphate soundness and Los Angles abrasion characteristics. Petrographic
analysis should be carried out and it will be necessary to check concrete aggregate for the
presence of deleterious constituents. The program was initiated but testing for alkalicarbonate reaction is a long term process.
6.11.3. Impervious Fill
Adequate quantities of impervious fill, suitable for cofferdam construction have been
located in the area of the dam sites. Test pitting showed these materials to be stratified, stiff,
moderately plastic silty clay with some silty sand bands. Adequate impervious materials are
available at each dam site. Laboratory testing carried out on this material considered the
moisture content, Atterberg limits, proctor density, specific gravity and mechanical gradation.
Sand content varies from 10% to 35%, the specific gravity is 2.6 and the average proctor
maximum dry density is 1790 kg/m3. The average optimum moisture content of 15% is higher
than the natural moisture content which varies from 4.5% to 13%.
6.12. Reservoir-Induced Earthquakes
In recent years, there have been many examples of small and medium sized earthquakes
occurring beneath or adjacent to recently filled reservoirs. Classic cases are the Koyna dam in
India, Kariba in Africa, and Krenasta in Europe (Campbell, 1981, Acres, 1982). Lesser cases
have occurred at Bajina Basta in Yugoslavia, Sringagarind in Thailand and elsewhere. There
is often a statistical correlation between the depth of water in the reservoir and the rate of
occurrence of foreshocks which generally precede these earthquakes, and this correlation is
assumed to signify a relationship between the filling of the reservoir and the occurrence of
seismic events (Campbell, 1981, Acres, 1982).
234
The mechanism by which filling of a reservoir might induce the occurrence of earthquakes
is not fully agreed by all authorities on the subject, but there is a general consensus that such
events can only happen in regions such as the Zagros belt which is subjected to significant
tectonic stress at the time the reservoir is filled. It is assumed that these stresses are released
or partially revealed by fault movement at depth during earthquakes, and that the filling of the
reservoir serves as a trigger to permit such movement on the fault (Acres, 1982).
The most likely explanation is that the raising of the water level causes an appreciable
increase in pore pressure in the rock beneath the reservoir, and that this increase in pore
pressure causes a decrease in the effective stress within a pre-existing plane of weakness in
the rock, such as a fault.
The resistance to shear stress is decreased and movement can occur in response to the
forces which are acting on such planes of weakness. Assuming such an explanation is valid,
then reservoir-induced seismicity could only occur in areas where pre-existing tectonic
stresses are of appreciable magnitude and where the new reservoir is of considerable depth.
Most cases of reservoir-induced seismicity occur in reservoirs at depths greater than 100 m
(Campbell, 1981, Acres, 1982). It is not yet possible to predict with any degree of reliability
whether a particular proposed reservoir will induce the release of tectonic stress in the form of
earthquakes. However it is possible to say that the more than 160 m depth of the reservoirs in
the area of research (especially at Karun-3 and Karun-4 with reservoir depths over 180 m)
will have many of the characteristics common to such cases.
In most cases of reservoir-induced seismicity, the shocks are of relatively small magnitude.
However, there have been a few events, notably at Koyna and Kariba, of magnitude 6.5 or
possibly even 6.8. No reservoir-induced earthquake larger than this has ever been recorded
(Campbell, 1981; Acres, 1982).
6.13. Conclusion and Recommendations
In general the following can be concluded based on the geological investigations in the area:
I.
Since Pliocene time the tectonic history of the investigated area produced intense
folding and thrusting of the outcropping sedimentary rocks. The continuous
convergence of the Arabian and Central Iran on Plate causes an uplifting of the belts
estimated to be about 1 mm/year (deep river valleys, higher alluvial terraces and fossil
beaches and uplift of historical channels) and results in intensive seismic activity
caused by basement high angle reverse faults. With regard to the magnitude of the
destructive earthquake a reactivation of folding-related discontinuities is likely to
occur. It was concluded that events larger than magnitude 7 Richter are not expected
in the Zagros seismotectonic province. Publications since the original 1978- 1979
Acers/ Appolonia study have confirmed this. The data published by Ambraseys and
Melville (1982) indicate that all events in the Zagros seismotectonic province are of
magnitude 6.8 or less.
II.
The Asmari Formation is of Oligo-Miocene age and comprise lithologically
massive/thick to medium bedded grey to light grey limestone, dolomitic limestone,
marly limestone, marlstone with thin interbeds of limestone and shale. Petrographical
analyses indicate Intrabiomicrite to Biodolomicrite, Wackestone to Packstone except,
in Salman Farsi which indicates locally Biointrasparite, Grainstone. Moreover,
dolomitization (Dolosparite) is locally well developed in the middle part at Salman
Farsi and Seymareh dam projects. This succession mainly constitutes the dam
232
foundation rocks and based on engineering geological aspects is commonly divided
into three rock units. Each of these has different strength and rock mass properties.
III.
The minimum/ maximum porosity values of the Asmari formation limestone,
according to microscopic quantitative method/point-counting analysis, are between
0.3% to 15.7%. In general the porosity values based on the Cherenyshev/Dearman
Classification indicate Medium to Extremely High porosity in the Asmari formation
limestones. Total porosity values of 35% and 13% are related to the Fracture/Channel
porosity types on the southern and northern flank sites respectively. This clearly
explains much more tilting (70°- 90°) or more curvature of strata in the south-western
flank of anticlines resulting from tectonic movements as well.
Asmari Formation limestone has been affected by karstification process and the caves,
stalagmites, stalactites, karstic channels and enlarged fissures are influenced by
aggressive water dissolution. Karst chimneys with apertures from a few centimetres to
a few metres have most frequently been detected. In addition, large caves with
volumes of thousands of cubic metres are present in some areas. The chemical
compositions of spring waters are calcium sulphate, sodium chloride and carbonate.
These compositions obviously indicate that, there are hydraulic connections between
the Asmari and Gachsaran formations with high karstification as well although the
field tests by MG. Co. (1984, 2003) do not confirm this connection! The closed
depression caves, sinkholes and collapse sinks in the Gachsaran Formation due to
chemical and physical dissolution of evaporite rocks are well developed. The Asmari
Formation limestones may be influenced by active mineral solutions originating in the
Gachsaran Formation and this is the main factor for the development of karst features
in the Asmari limestones especially in upper and middle parts. The interaction
between the future reservoir and the karst at the dam sites can be quantitatively
appreciated by extensive injection and tracing tests. The acquired results will help in
the design, to appreciate the costs and test the efficacy of the grout curtain. The water
tightness of the dam sites and reservoirs should be investigated in more detail to
recognize karstified zones in the Asmari Formation and Fars Group, especially the
Gachsaran Formation, in addition to contact zones between the two formations.
IV.
Tectonic conditions in the area have caused the creation of different discontinuities in
the rock mass. These discontinuities include fissures, joint sets, major joints, fractures
and faults in addition to the bedding planes. Fracture systems in the Asmari Formation
were investigated from exploratory boreholes and surface fracture studies. The
similarity between the fracture density and curvature rate of strata at construction sites
coincide well with the asymmetrical fold structures with different curvature rates in
the Zagros region. It can also be expected that there is a direct relationship between
fracture intensity and curvature rate in fold structures in the region. This is obviously
indicated by the RQD, RMR and GSI values. Due to compressional stress, more
reverse faults and tectonic disturbances can be observed in the southern flanks of fold
structures such as at Karun-3 and Karun-4 dam sites.
V.
The dip direction of the Asmari limestones at two dam sites at the northern and
southern flanks are almost perpendicular to the dam valleys and will produce two
different conditions of adjusting factors according to the main discontinuity
orientation, if the bedding planes are considered to be the main discontinuity set.
Adjusting factors for the stability (RSTA), according to joint orientation (Romana,
233
2003) for the northern flanks are fair to very favourable but in the southern flanks,
where the Karun-3 and Karun-4 dams are located, this factor is a fair condition.
VI.
Generally, the stability of a reservoir rim depends on parameters, such as reservoir
water level, the nature of formations which have most contact with the reservoir water
and their dip with respect to the reservoir. Planar and rotational sliding of rocks
normally after impounding of reservoirs can be expected. These instabilities in the
rock mass commonly occur around the reservoir walls, but only deep seated sliding
surfaces can produce destructive hazards at dam projects. Therefore identification of
such cases, in addition to the provision of a landslide hazard zonation (LHZ) at
reservoirs will be necessary (Anbalagan and Gopta, 1995). It should be stated that the
potential of sliding on the contact between the Asmari and Pabdeh formations after
reservoir impounding, will increase, where the Asmari limestone commonly
constitutes high angle cliffs around the reservoir due to its rigidity. The highly
permeable Gachsaran/Razak formations (mainly evaporites and marl) will also be
highly prone to instability due to tectonic disturbances, solubility and high flexibility
of the rock mass. The sliding failures in this case will commonly be circular or
rotational failures. Water absorption by interbedded marls after reservoir impounding
will influence rock sliding towards the reservoir. In this regard, the active tectonism of
the region can easily activate and trigger such sliding. Furthermore, all types of rock
mass failure such as wedge, toppling; planar failures and rockfalls, adjacent to the dam
locations are expected. Slope stability analysis indicate Unstable to Partially stable of
rock slopes on both flanks of the dams.
Forcasting of rock slope instability by instrumentation and monitoring/remote
monitoring will be needed especially at the dam walls. Obtaining accurate
measurements of the rock face can be a major challenge when assessing risk on very
large rock slopes, which are often difficult to access and potentially dangerous.
However traditional discontinuity measurements such as scanline, cell mapping and
geologic structure mapping have several major disadvantages (Priest and Hudson,
1981, Priest, 1993, Hack, 1998). Conventional techniques, such as vertical aerial
photography and extrapolation from topographic maps, provide very poor data sets
due to the small footprint of a steep slope. Some success have been achieved with
oblique photography, but this approach requires considerable post-processing based
upon large numbers of tie points.
Impact sentinel sensors check the status of rockfall protection systems and set off an
alarm if limit values are exceeded. Hence, potential accidents involving personal
injuries or economic damage can be effectively prevented. This system is specifically
designed for difficult access places where wiring or power supply is not available and
where it could only be implemented at great expense. Impact sentinel can be used
permanently, for instance, in remote areas or temporarily, to help secure construction
sites. (Geobrugg AG. Protection system, Impact Sentinel- Remote Monitoring of
Rockfall Barriers. 2009).
More recently Terrestrial Laser Scanning (TLS) has provided a method of rapidly
capturing morphological data. TLS instruments are designed to record surfaces under
a wide range of environmental conditions and can operate at ranges of up to about
2,000 m (Nagihara et al. 2004). Aoki et al. (1997) report using TLS to monitor
volcanic cone deformation; Nagihara et al. (2004) for the morphometric analysis of
sand dunes; Fardin et al. (2004) for rock surface roughness and Rowlands et al. (2003)
for landslide analysis.
231
VII.
As the dams will be founded on the Asmari Formation and considering this formation
is weathered and crushed at surface, it is estimated that the depth of the materials to be
removed ranges from 1m to 10 m with an average of 3-5 m. The thickness of the
alluvium to be removed from the river beds commonly ranges from 25 to 50 m. After
the removal of weathered rock, the foundation will rest on sound rock. In addition to
the above mentioned, attention should also be paid to dam abutments. Exploratory
adits and drilling investigation borehole data, indicate some low strength beds which
have been eroded and then filled in by secondary materials. These materials should be
removed and the fill materials along faults (brecciated zones and gouge materials) in
the foundation rocks should be replaced by suitable concrete aggregate.
VIII.
In general, the geological and geotechnical investigations of the Asmari Formation
limestone showed the rock to be fairly suitable foundation material for dam
construction in the Zagros region. According to geological assessments (Table 6.5 and
Figure 6.18) it can be concluded that the engineering rock mass conditions at the
Karun-3 and Karun-4 dams are;
 Blocky- Very Well Interlocked and Good (B/G) to
 Blocky Disturbed/Seamy and Fair (BD/F)
The GSI values are between 35 to 65.
The engineering rock mass conditions at the Marun and Seymareh dams are;
 Blocky- Very Well Interlocked and Good (BG) to
 Very Blocky- Interlocked and Fair (VB/F)
The GSI values are between 45 to 70.
In the case of Salman Farsi however it is relatively variable due to extensive development of
marlstone, marly limestone with thin interbedded limestone in the lower and upper units on
the one hand and extensive development of dissolution and karstic features on the other hand.
This results in a wide range of GSI values from;
 Blocky- Very Well Interlocked and Good (BG) to
 Blocky Disturbed/Seamy and Poor (BD/P)
The GSI values are between 25 to 65.
235
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APPENDIX 1
Petrographic Description of the Various Units of the Asmari Formation in Karun-3 Dam
Lower Asmari (As..1)
A (Crossed nicols)- Pelmicrite, Wackestone, Coarse subhedral to euhedral cement calcite crystals (Drusy calcite spar) within fracture cavity
well developed, it is a characteristic pore-filling cement with an increasing crystal size towards the cavity centre one further feature of drusy
calcite spar is the presence of growth zones, Χ10.
B- Intrabiomicrite, Wackestone. Vuggy and intraparticle porosity, with various shaped micritic and microsparitic intraclasts. Foraminiferal
chambers mainly filled by micritic and microsparitic calcite cement. The organic constituents are mainly Planktonic Foraminifera with axial
and tangential sections such as Globigerina sp., Ostracoda shell and skeletal debris, Χ10.
C- Intrabiomicrite, Wackestone to Packstone. Vuggy porosity partly filled by sparry calcite cement with irregular shaped of small
microsparitic intraclasts. The recognizable organic components are Foraminifera shell such as Rotalia sp. Bivalve shell fragment showing a
finely prismatic calcite microstructure, small circular black structures are microborings, Echinoid shell fragments and Echinoid spines in
cross section. The Echinoid spines wall zone consists of wedge shaped radial elements which widen toward the periphery, Dasyclad green
calcareous Algae and some small skeletal debris, Χ10.
D (Crossed nicols) - Intrabiomicrite, Packstone. Fracture porosity which filled partly by microsparitic calcite cement. With irregular shaped
of micritic and microsparitic intraclasts. The organic components are Echinoid spines in oblique section and small skeletal debris, Χ10.
Upper Asmari (As..2)
A- Intrapelmicrite, Wackestone. Vuggy porosity partially filled by microsparitic calcite cement, with subangular sparitic intraclasts. Locally
recrystallization of micrite to microsparry calcite, Χ10.
B- Biomicrite, Mudstone. Micritic limestone, Poor porosity, with subrounded microsparitic intraclasts. The organic constituents are mainly
Planktonic Foraminifera such as Globigerina sp., Χ10.
C- Biointramicrite, Wackestone. Poor porosity with irregular shaped of micritic and microsparitic intraclasts. Locally recrystallization of
micrite to microsparry calcite cement. The organic components including Foraminifera shell such as Miogypsina sp. and abundant minute
debris belonging to Planktonic Foraminifera (Globigerina sp.), Χ10.
D- Biointramicrite, Wackestone. Fracture and vuggy porosity, conjugate set of fracture veins partly filled by microsparry calcite. With
various shaped of micritic and microsparitic intraclasts. The organic constituents including some Bivalve shell fragments, Χ10.
Lower Asmari (As.1)
A
C
B
D
Upper Asmari (As.2)
A
A
B
B
C
211
D
APPENDIX 2
Petrographic Description of the Various Units of the Asmari Formation in Karun-4 Dam
Lower Asmari (As.1)
A- Intrapelbiomicrite, Packstone. Intraparticle and fracture porosity that partially filled by micritic and microsparitic calcite cement. With
sub angular and irregular shaped of micritic intraclasts. He recognized fauna are mainly Foraminifera shells such as Operculina sp. (axial
and sub equatorial sections), Ditrupa sp. (transverse section) and small skeletal debris, Χ10.
B (Crossed nicols) – Biointramicrite, Wackestone. Vuggy porosity that in some small parts filled by microsparitic calcite cement. With
various shaped of micritic to microsparitic intraclasts. The organic constituents are Foraminifera shell such as Operculina sp. and small
skeletal debris, Χ10.
C (Crossed nicols) – Biopelmicrite, Wackestone. Fracture porosity that filled by coarse blocky/ granular calcite cement, Vuggy porosity. The
organic elements are Echinoid Shell fragments, calcareous Red Algae and some rare Foraminifera tests, Χ10.
D - Biointramicrite, Packstone. Fracture/ Channel porosity. With irregular distributed subangular sparitic and microsparitic intraclasts. The
recognized organic components are Foraminifera shell such as Lepidocyclina sp., Elphidium sp., Echinoid shell fragments and small skeletal
debris, Χ10.
Middle Asmari (As.2)
A- Dolomicrosparite. Fracture/ Intercrystalline porosity, the micritic cement relatively replaced by dolomicrosparitic granular cement. The
coarse rhombohedral crystals of dolomite due to dolomitization are relatively well developed specially in the cavities. The bioclasts are
composed of some Echinoid shell fragments, Χ10.
B- Biodolomicrosparite, Wackestone. Intercrystaline porosity. Dolomitization extensively developed throughout the rock, the coarser
rhombohedral crystals of dolomite locally growth in cavities. The bioclasts are partly affected by dolomitization and comprised of rare
Foraminifera shell such as Miliolide (Quinqueloculina) and Rotalia sp., Χ10.
C- Biointramicrite, Wackestone. Vuggy porosity. With irregular shaped of dark micritic intraclasts. The matrix locally influenced by
dolomitization (small rhombohedral crystals). The organic constituents are mainly Foraminifera shell such as Peneroplis sp.,
Quinqueloculina, Biloculina (Miliolide) and skeletal debris, Χ10.
D- Biointramicrite, Wackestone. Vuggy porosity. With micritic intraclasts. The matrix locally changed to microsparitic calcite cement. The
identifiable organic components are mainly Foraminifera such as Austrotrillina sp., Quinqueloculina, Biloculina (Miliolide) and some
skeletal debris, Χ10.
Upper Asmari (As.3)
A, B, C, D- Intrabiomicrite, Mudstone to Wackestone. Fracture/ Vuggy porosity, that partly filled by microsparitic calcite cement. With rare
and small rounded intraclasts. The Foraminiferal chambers also filled with sparry calcite cement. The recognizable microfauna are mainly
Planktonic Foraminifera shell such as Globigerina sp., Χ 10.
Lower Asmari (As.1)
A
B
C
D
Middle Asmari (As.2)
CA
D
B
C
D
Upper Asmari (As.3)
E
A
F
C
G
B
215
D
APPENDIX 3
Petrographic Description of the Various Units of the Asmari Formation in Marun Dam
Lower Asmari (As.1)
A- Intrabiomicrite, Packstone. With subangular microsparitic intraclasts, Intraparticle and vuggy porosity. Organic constituents are
Asterigerina sp., Rotalia sp., Miogipsina sp., Biloculina, calcareous Red Algae and some skeletal fragments, Χ10.
B- (Crossed nicols) - Biointramicrite. Packstone, high porosity, vuggy to channel, cavities filled partly by microsparitic calcite cement, the
identifiable organic components are Echinoid shell fragments, Χ10.
C- Intrabiomicrite, Wackestone. Cavities filled by coarse sparry calcite vein. Organic constituents are Foraminifera shell comprises of
Peneroplis sp., Biloculina (Miliolide). All foraminifer's chambers are filled by microsparry calcite cement, Χ10.
D- Intrabiomicrite, Packstone. With some irregular shaped of microsparitic intraclasts. Vuggy and Intraparticle porosity, the porosity partly
filled by calcite cement. Organic components are Foraminifera species comprises of Haplophragmium sp., Biloculina and some skeletal
debris of Pelecypoda shell, Χ10.
Middle Asmari (As.2)
A- Pelbiomicrite, Packstone. Vuggy to channel porosity partly filled by sparry calcite cement. Organic constituents comprises of Peneroplis
sp., Calcareous Algae and skeletal debris, Χ10.
B- Biomicrite, Wackstone. Vuggy porosity, cement locally changed to the microsparry calcite (sparry patches). Organic components are
Foraminifera shell such as Biloculina, Quinqueloculina, and some skeletal debris, Χ10.
C- Biomicrite, Wackestone. Vuggy porosity, micritic cement partly changed to microsparry calcite (sparry patches), organic constituents are
comprise of Calcareous Red Algae and skeletal debris, Χ10.
D (Crossed nicols)- Biomicrite, Wackestone. Fenestral porosity, some cavities are filled by microsparry calcite cement. Organic constituents
are Calcareous Algae and some skeletal debris, Χ10.
Upper Asmari (As.3)
A- Intrabiomicrite, Wackestone. Vuggy porosity, organic constituents are Echinoid shell and spines, and Foraminifera shell, Χ10.
B- Pelbiomicrite, Wackestone. Fracture porosity, partly filled by coarse sparry calcite cement. The identifiable Bioclasts are skeletal debris,
Χ10.
C- Pelbiomicrite, Wackestone. Vuggy and Intraparticle porosity. The identifiable organic constituents are Foraminifera shell such as
Dendritina sp. (equatorial section), Quinqueloculina, and fragments of Echinoid shell, Χ10.
D (Crossed nicols), - Pelbiomicrite, Wackestone. Fracture porosity. With small microsparitic intraclasts, bioclasts are skeletal debris, Χ10.
Lower Asmari (As.1)
G
H
A
B
G
C
H
D
B
Middle Asmari (As.2)
C
A
E
B
F
C
G
D
Upper Asmari (As.3)
CA
DB
F
216
C
D
APPENDIX 4
Petrographic Description of the Various Units of Asmari Formation in Seymareh Dam
Lower Asmari – As.1
A (Crossed nicols), – Intrabiomicrite, Packstone. Vuggy porosity, with irregular shaped of micritic intraclasts, the cavities partly filled by
sparry calcite cement. The identifiable organic constituents are Foraminifera such as Archaias sp., Quinqueloculina, Triloculina (Miliolides),
Calcareous Red Algae, and some skeletal debris, Χ 10.
B- Intrabiomicrite, Packstone. Vuggy porosity, the organic constituents are Corals (transverse section) and some skeletal debris, the coral
chambers are filled by micritic and sparry calcite cement, Χ 10.
C- Intrabiomicrite, Packstone. Vuggy porosity, cavities filled by coarse blocky/granular calcite cement, with subrounded microsparitic intraclasts.
Bioclasts are Foraminifera such as Rotalia sp. (axial section), Ditrupa sp. (worm tube, Echinoid shell and Calcispongia fragments, Χ 10.
D- Pelbiomicrite, Packstone. Vuggy porosity partly filled by sparry calcite cement, with a few micritic pellets. The organic elements are
comprised of Pelecypoda shell, Echinoid shell, Echinoid spines, Hydrozoans (spongiomorphids) fragments, Calcareous Algae, Foraminifera
such as Rotalia sp. and skeletal debris, Χ 10.
Middle Asmari – As.2
A- Biointramicrite, Packstone. Vuggy porosity, with irregular shaped of micritic and microsparitic intraclasts, Organic constituents are
Foraminifera shell such as Operculina sp. (sub equatorial section)
and skeletal debris, Χ10.
B- Biodolomicrite, Wackestone. Dolomitization extensively developed throughout the rock even bioclasts partly impressed by dolomitization
process. Bioclastic elements are comprised of Calcareous Red Algae and Foraminifera such as Lepidocyclina sp. (sub axial section), Χ10.
C- Intrapelbiomicrite, Wackestone to Packstone. With rounded to sub rounded microsparitic intraclasts. The identifiable organic components
are Echinoid shell and spines, Hydrozoans (spongiomophids) fragments, Pelecypoda shell, Quinqueloculina (Miliolide) and skeletal debris, Χ10.
D- Intrapelbiomicrite, Wackestone to Packstone. With irregular shaped of micritic and microsparitic intraclasts. The identifiable organic
components are Pelecypoda shell fragments, Echinoid, shell, Hydrozoans (spongiomophids) fragments, Χ 10.
Upper Asmari – As.3
A – Intrapelbiomicrite, Wackestone. Vuggy porosity, some cavities filled by coarse sparry calcite cement. Micritic cement locally
recrystalized to microsparry calcite. Organic constituents are some skeletal debris, Χ10.
B- Intrapelbiomicrite, Wackestone to Packstone. Vuggy and fracture porosity that partly filled by sparitic calcite cement. With irregular
shaped of dark micritic intraclasts. The organic components are Foraminifera such as Quinqueloculina (Miliolide), Echinoid shell fragments
and skeletal debris, Χ10.
C- Pelbiomicrite, Packstone. Vuggy to fracture porosity partly filled by sparitic calcite cement. With sub rounded microsparitic intraclasts.
Organic constituents are Foraminifera such as Borelis sp., Echinoid shell fragment, spines, calcareous Red Algae and some skeletal debris, Χ10.
D- Intrapelbiomicrite, Packstone. Fracture porosity partly filled by s parry calcite cement. With irregular shaped of micritic intraclasts. The
organic elements are composed of Foraminifera such as Borelis sp. and some Planktonic species, Hydrozoans (spongiomorphids)
fragments,Χ10.
Lower Asmari (As.1)
A
B
C
D
Middle smari (As.2)
A
B
C
D
Upper Asmari (As.3)
A
B
C
217
D
APPENDIX 5
Petrographic Description of the Various Units of Asmari Formation in Salman Farsi Dam
Lower Asmari (As.1)
A- Biomicrite, Packstone. With small vuggy and fenestral porosity, some of them filled with micro sparry calcite cement. Organic
components are mainly Benthic Foraminifera such as Operculina sp., Heterostegina sp., Rotalia sp (axial sections). fragments of calcareous
Red Algae and Echinoid shell debris, Χ10.
B- Biomicrite, Boundstone. With fenestral porosity, channel porosity filled by blocky micro sparry calcite cement. Organic materials are
Calcareous Red Algae and some skeletal debris, Χ10.
C- Pelmicrite, Wackestone. With Vuggy porosity, fractured porosities are filled with coarse sparry calcite cement, Χ10..
D- Biopelmicrite, Wackestone. With vuggy porosity. Organic components are Foraminifera shells also some planktonic species and
fragments of Echinoid shell, Χ10.
Middle Asmari (As.2)
A- Biointrapelmicrite, Wackestone. Vuggy and intraparticle porosity. With irregular shaped of microsparitic intraclasts. Organic constituents
are Foraminifera shell such as Operculina sp. (axial section) some porcelaneous tests and skeletal debris, Χ10.
B (Crossed nicols)- Intrapelbiomicrite, Packstone. Channel porosity, some cavities are filled with microcrystalline quartz. With irregular
shaped of microsparitic intraclasts. The identifiable organic components are some small Foraminiferal shell and skeletal debris, Χ10.
C- Biodolomicrite, Wackestone. Micro vuggy porosity. Dolomitization relatively extended throughout the rock (coarse rhombohedral
crystals of dolomite). Organic constituents are Echinoid fragments and some skeletal debris, Χ10.
D- Intrabiosparite, Grainstone. With vuggy and intraparticle porosity. The identifiable organic components are Foraminifera that comprised
Peneroplis sp. (equatorial section), Miliolides (Quinqueloculina) and some skeletal fragments, Χ10.
Upper Asmari (As.3)
A- Dolopelmicrite, Wackestone. Vuggy and channel porosity. Micritic cement partly changed to rhombohedral crystals of dolomite that
scattered throughout the rock, Χ10.
B- Biodolomicrite, Wackestone. Vuggy porosity, with chert stains, Dolomitization extensively changed rock matrix (granular and uniform).
Foraminifer's chambers are filled by microsparry calcite cement. Bioclasts peripherally changed to dolomite. Organic components are
Foraminifera such as Nummulites sp. and Operculina sp. (axial sections), Χ10.
C- Biointrasparite to Biointramicrite, Packstone to Grainstone. Vuggy porosity, the identifiable organic elements are Foraminifera such as
Archaias sp., Quinqueloculina, Biloculina and Mollusk shell fragments, Χ10.
D- (Crossed nicols), H (Ordinary light) - Fault Microbreccia, Breccia porosity, from thrust zone (Dareh Siah Fault) where the Asmari
Formation thrusted on Razak Formation. Microbreccia is composed of clasts that are smaller than 1.0 mm but greater than about 0.1 mm,
with irregular shaped of angular to subangular intraclasts that cemented partly by fine blocky calcite cement.
High porosity (19.40 %), cavities partly filled by microsparry calcite cement, Χ10.
Lower Asmari (As.1)
A
C
B
D
Middle Asmari (As.2)
A
C
B
D
Upper Asmari (As.3)
A
B
C
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D
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