TABLE OF CONTENTS

1. Introduction ......................................................................................... 6
1.1 Project ................................................................................................................................................. 6
1.2 Organization of the Report .............................................................................................................. 7

2. References .......................................................................................... 7

3. Project Information ............................................................................. 8

3.1 Horizontal Alignment ........................................................................................................................ 8
3.2 Vertical Alignment ............................................................................................................................. 8

4. Regional Geology ................................................................................ 9

4.1 Temperature and Climate .............................................................................................................. 10
4.2 Seismicity.......................................................................................................................................... 10

5. Geotechnical Investigation............................................................... 11
5.1 Existing Information ........................................................................................................................ 11
5.1.1 Boreholes .................................................................................................................................. 11
5.1.2 Laboratory and Field Test ...................................................................................................... 16

6. Results ............................................................................................... 17
6.1 Laboratory Test Results ................................................................................................................. 17
6.1.1 Grain Size Distribution ............................................................................................................ 17
6.1.2 Natural Moisture Content ....................................................................................................... 17
6.1.3 Atterberg Limits ....................................................................................................................... 17
6.1.4 Bulk Density .............................................................................................................................. 18
6.1.5 Triaxial Testing ......................................................................................................................... 18
6.1.6 Chemical Aggressivity and Corrosion ................................................................................. 18
6.1.7 Tests on Rock........................................................................................................................... 18
6.2 Field Test Results ............................................................................................................................ 18
6.2.1 SPT ‘N’ Distribution .................................................................................................................. 18
6.2.2 Permeability Test Results ...................................................................................................... 19
7. Geotechnical Assessment ................................................................ 19
7.1 Soil Parameters ............................................................................................................................... 20
7.1.1 Consistency based on SPT Values ...................................................................................... 20
7.1.2 Bulk Density .............................................................................................................................. 20
7.1.3 Permeability .............................................................................................................................. 21
7.1.4 Strength and Stiffness Parameters ...................................................................................... 22
7.1.4.1 Undrained Behavior ............................................................................................................. 22
7.1.4.2 Drained Behavior ................................................................................................................. 23
7.2 Geotechnical Design Parameters for Soil ................................................................................... 24
7.3 Chemical Aggressivity and Corrosion – Soil and Groundwater .............................................. 24
7.4 Rock Parameters ............................................................................................................................. 25
7.4.1 Classification of Rock ............................................................................................................. 25
7.4.2 UCS Test Results of Rock ...................................................................................................... 27
7.4.3 Point Load Strength Index Test Results of Rock ............................................................... 27
7.4.4 Rock Mass Rating System (Bieniawski)................................................................................ 28
7.4.5 Geological Strength Index (GSI) ............................................................................................ 29
7.4.6 Deformation Modulus of Rock Mass .................................................................................... 31
7.4.7 Lugeon Test .............................................................................................................................. 31

8. Conclusion and Recommendations ................................................. 32

8.1 Groundwater Conditions ................................................................................................................ 32
8.2 In-situ Conditions ............................................................................................................................ 32
8.3 Settlement Predictions .................................................................................................................. 32
8.4 Design Parameters ......................................................................................................................... 34

Appendix – A ........................................................................................... 36
Plots for Soil ............................................................................................................................................. 36
A1. SPT vs Depth ..................................................................................................................................... 37
A2. Coefficient of permeability vs Depth ............................................................................................ 38

Appendix – B............................................................................................ 39
Plots for Rock ........................................................................................................................................... 39
B1. RQD vs Depth .................................................................................................................................... 40
B2. UCS of intact rock vs Depth ............................................................................................................ 41
B3. Point load index vs Depth ................................................................................................................ 42
B4. Elastic Modulus of intact rock vs Depth ....................................................................................... 43
B5. Coefficient of Permeability vs Depth ............................................................................................ 43

Appendix – C ........................................................................................... 44

Appendix – D ........................................................................................... 45
LIST OF FIGURES:
Figure 1: Map showing various Geological Units (after GSI……) ............................................................................. 10
Figure 2: Relationship between Φ and SPT N Value (IS: 6403 – 1981) ................................................................. 23

LIST OF TABLES:

Table 1 : Tentative Civil Contract Packages ............................................................... 7

Table 2 : Underground Tentative Civil Contract Package T - 104 Alignment ........... 8
Table 3 : Existing Information: Geotechnical Investigation Reports ....................... 11
Table 4 : Borehole Details ........................................................................................... 11
Table 5 : Existing Information: Field and Laboratory Testing .................................. 16
Table 6 : Determination of Parameters from SPT Values (CIRIA Report 143) ........ 19
Table 7 : Permeability values for soil layers based on Test Results........................ 19
Table 8 : Consistency based on SPT values from CIRIA Report 143 ....................... 20
Table 9 : Unit Weight of Soil according to BS 8002: 1994 ......................................... 20
Table 10 : Range of Permeability values for different soils (FHWA) ........................ 21
Table 11 : Relationship between compressive strength and SPT Value and
consistency of saturated Cohesive Soils (from Terzaghi & Peck, 1967) ................ 22
Table 12 : Value Ranges for Poisson’s Ratio (from Bowels-Fifth edition) ............... 22
Table 13 : Classification based on Sulphates in soil and ground water as per IS:
456 ................................................................................................................................ 24
Table 14 : Classification based on Chlorides content as per IS: 456 ....................... 24
Table 15 : Classification based on PH values ............................................................. 24
Table 16 : Classification of rock based on weathering grades (IS 4464) ................ 25
Table 17 : Classification of weathering grades based on CR and RQD ................... 26
Table 18 : Classification of weathering grades based on RQD ................................ 27
Table 19 : Average UCS (Intact Rock) Test Results .................................................. 27
Table 20 : Average Is(50) Test Results ........................................................................ 28
Table 21 : Rock Mass Classification based on RMR (IS :13365 (Part 1)-1998) ........ 29
Table 22 : Representative values of GSI for different rock grade (IS 13365 Part 4)
...................................................................................................................................... 30
Table 23 : Rock mass classification ........................................................................... 30
Table 24 : Stiffness Parameters of Rock ................................................................... 31
Table 25 : Indicative rock permeability’s (Look 2007) .............................................. 32
Table 26 : Generalized Design Parameters for Soil .................................................. 34
Table 27 : Design Parameters for Rockmass ............................................................ 35
1. Introduction

Bangalore is the Information technology capital of India. Bangalore Metropolitan Region (BMR) is
one of the fastest growing regions in India. BMR is experiencing a rapid growth in population and
employment and this trend is expected to continue with immigrants from the hinterland of
Karnataka’s as well as from all parts of the Country attracted by job opportunities offered in
Bangalore.

In order to improve the overall traffic and transportation scenario in Bangalore and to cater the
future travel needs, the Government of Karnataka (GOK) through Bangalore Metro Rail Corporation
Limited (BMRCL) has undertaken several studies and identified metro model as efficient,
economically viable, secure and environment friendly mass transport system.

The DMRC submitted the DPR for Phase-I of the Namma Metro project to the BMRCL in May 2003,
but the final approval on a scheme come in April 2006. The DPR prepared by DMRC envisaged a
33 km (21 mi) elevated and underground rail network with 32 stations for Phase-I of the project. The
proposed gauge was standard gauge. The rationale for the metro includes reduced journey times,
cutting fuel use, accident reduction and lower pollution. Phase-I, Reach 1(east), Reach 2 (west),
Reach 3 & 3A (north), and reach 3B are operational, whereas Reach 4, 4A and UG1 Easts to West
and North to South will be opened soon.

Meanwhile, In 2011 The State Government appointed DMRC for carrying out detailed project report
(DPR) for Phase-II. The high power committee (HPC), in July 2011, gave in-principle clearance to
proceed with Phase-II. The Karnataka government gave in-principle approval to Phase II of the
Namma Metro project on 3 January 2012. Phase II was as well cleared by the expenditure finance
committee (EFC) in August 2013. The Union cabinet in 2014 approved plans for phase II.

Currently BMRCL has appointed Interim Design Consultants (IDC) for requisite services for the
preliminary designs /tender design and other related preparatory activities required for the purpose
of the Bidding for the Civil Works for the Red Line, Reach – 6 from Dairy Circle to Nagawara
underground stretch. IDC has also been asked to do the Detail design of M&E services for Reach 6.

BMRCL has appointed AECOM as Interim Design Consultant (IDC) for Civil, Architectural and E&M
Works of underground section and stations – total 13.070km and 12 underground stations, starting
from dairy Circle to Nagawara of Reach 6, for proposed Phase-II of BMRCL Project. The IDC carried
out site specific studies and has studied geotechnical data given by BMRCL.

1.1 Project

The Metro line (Phase-II) from Dairy circle to Nagawara Reach 6 corridor extends in South - North
direction for a stretch of 13.79 km, fully underground. The proposed stretch includes 12 stations.
The stations being:

 Dairy Circle

 MICO Industries

For internal use only

  Langford Town

 Vellara Road

 M.G. Road

 Shivaji Nagar

 Cantonment

 Pottery Town

 Tannery Road

 Venkateshapura

 Arabic College

 Nagawara

1.2 Organization of the Report

The construction of Bangalore Metro phase-II has been divided into four contract packages as
described in Table 1. This report has to be treated as a standalone GIR for Under Ground Civil
Contract Package T-104. The Geotechnical data available from the various investigations carried
out till date has been reviewed and analyzed to arrive at design parameters for Civil package T-104.

Table 1 : Tentative Civil Contract Packages

Package Description

BMR/PH-II/R6/UGC – 103 Dairy Circle Ramp at southern end of Vellara Road station

BMR/PH-II/R6/UGC – 104 Vellara Road station to southern end of Cantonment station

BMR/PH-II/R6/UGC – 105 Cantonment station to southern end of Venkateshapura station

BMR/PH-II/R6/UGC – 106 Venkateshapura station to Ramp at northern end of Nagawara

station

2. References

 IS: 456-2000 (Reaffirmed 2005): Plain and Reinforced Concrete.

 The Standard Penetration Test (SPT): Methods and Use-CIRIA Report 143 1995.
 IS: 6403-1981: Code of Practice for Determination of Bearing Capacity of Shallow
Foundation.
 J. E. Bowels, Foundation Analysis and Design – Fifth Edition.
 Handbook of Geotechnical Investigation and Design Tables by Burt Look, 2007
 BS 8002-1994: Code of Practice for Earth Retaining Structures.
 Estimating the Strength of Jointed Rock masses by Zhang (2010).

For internal use only

  CIRIA-R143-The-Standard-Penetration-Test-SPT-Methods-and-Use-1995
 IS: 4464-1985, Code of practice for presentation of drilling information and core
description in foundation investigation.
 IS: 8764 - 1998, Method for determination of point load strength index of rock.
 Bieniawski, Z.T. 1973. Engineering classification of jointed rock masses. Trans S. Afr.
Inst. Civ. Engrs 15, 335-344.
 IS:13365 (Part 1): 1998. Quantitative classification systems of rock mass – guidelines,
further amended in 2008
 IS 13365 (Part 4): Draft, Quantitative classification systems of rock mass – Guidelines Part 4
Geological Strength Index (GSI).

3. Project Information

From Dairy circle to Nagawara, the alignment follows south north direction for a stretch of 13.79
km. The entire alignment is divided into 4 packages as shown in Table 1.

3.1 Horizontal Alignment

The horizontal alignment with bore hole locations for package BMR/PH-II/R6/UGC – 104, is shown in
Appendix – C.
Table 2 : Underground Tentative Civil Contract Package T - 104 Alignment

Up line Length of
Package Chainage (m) Package Description
Start End (m)

Vellara Road station to southern

BMR/PH-II/R6/UGC – 104 11128 14957 3829
end of Cantonment station

3.2 Vertical Alignment

The vertical rail alignment in Package T-104 passes through soil (silty sand/sandy silt) and rock
(granitic gneiss). The running tunnels within this package will get generally embedded in rock strata
of grade II, III and IV/V and partially in soil strata along the alignment. However at some locations,
tunneling will be in mixed ground i.e. soil/grade-II/III/IV/V rock is anticipated. The classification of
rock based on weathering grade is further detailed in section 7.4.1. The geological profile along the
alignment is shown in Appendix - C.

For internal use only

4. Regional Geology

Geology wise, Bangalore district shows dominant presence of ‘Archaean’ crystalline rocks
comprising Peninsular Gneissic Complex with small patch of hornblende schist in the northern part
and intrusive Closepet granites all along the western part of the district. The gneissic rocks
are reported to be in the age range of 2.6 to 3.0 billion years. They are essentially grandioritic and
granitic in composition formed due to several tectono-thermal events with large influx of sialic
materials representing remobilized parts of an older crust with abundant additions of younger
granitic materials. The Peninsular Gneissic Complex constitutes the basement for schist belts that
are largely basaltic in composition and characterized by gold mineralization which is noticed in
Kolar Gold Fields located in adjacent Kolar district to the east of Bangalore distirict. Small stretches
comprising unconsolidated sediments are also noticed in Channapatna and Devanahalli.

For internal use only

 Figure 1: Map showing various Geological Units (after GSI……)

The soil overburden generally is dominated by silty sand /residual silt and shows presence of clay
as a nominal interstitial binder. Overburden in upper layers is generally in loose /medium compact
condition especially in areas with high water table. The overburden thickness is variable and is
reflective of typical differential weathering that has occurred over a prolonged period. This is
followed by completely weathered rock and highly weathered rock. The geological map of
Bangalore district taken from Geological Survey of India (2000) and the same is presented in Figure
1.

4.1 Temperature and Climate

Bangalore is situated at an altitude of about 900m above the mean sea level. It is located about
1150 kilometers south of tropic of cancer. The mean temperature varies from 170ºc to 380ºc. The
area has the benefit of northeast and southwest monsoons. The annual rainfall is about 760mm.
The weather is neither humid nor dry. The soil formation is due to physical weathering of parent
rock caused by temperature changes accompanied by chemical transformation.

4.2 Seismicity

Bangalore falls under Zone II of Seismic Zonation Map of India as per IS: 1893 (Part I) - 2002.
Recent earthquakes that occurred close to Bangalore were in the range of 2.0 to 5.5 on Richter

For internal use only

scale. On January 29, 2001, an earthquake with a magnitude of 4.3 on the Richter scale hit the
Mandya area; with its epicenter about 35 km south of Bangalore.

5. Geotechnical Investigation

Geotechnical Investigations have been carried out at various stages, a brief summary of which is
given below:

5.1 Existing Information

The ground investigation information available till date is shown in Table 3.

Table 3 : Existing Information: Geotechnical Investigation Reports

Report Document GI Contractor Author

Geotechnical investigation for the

proposed construction of stations and M/S CIVIL-AID
tunnels for Bangalore metro project Part 1,2&3 Technoclinic BMRC(2014)
Phase II (Swagath - Pottery ) Pvt. Ltd.

Station locations

Geotechnical investigation for Viaduct & Pier locations

(Volume-I,II) M/S SECON Pvt.
stations for section R6 underground line BMRC(2014)
Ltd.
(Nagawara-Pottery Town)
Permeability Test
Results

5.1.1 Boreholes

A summary of borehole results along package BMR/PH-II/R6/UGC – 104 alignment is presented in

Table 4.
Table 4 : Borehole Details

Sl. Total depth

Location BH No. EASTING NORTHING R.L SOIL WR/HR
No. drilled

1 VR-1 782800.614 1434568.096 908.2 27 0 27

Vellara Road
2 Station VR-2 782797.264 1434586.529 908.12 27 0 27

3 VR-3 782796.912 1434607.117 908.29 15 12 27

4 VR-4 782796.23 1434629.429 908.37 18 10 28

5 VR-5 782794.257 1434654.683 908.35 16.5 11.5 28

Vellara Road
6 Station VR-6 782815.582 1434652.212 908.61 28 0 28

7 VR-7 782795.76 1434697.394 908.66 9 9 18

8 VR-8 782816.227 1434671.999 908.59 21 7 28

For internal use only

Sl. Total depth
Location BH No. EASTING NORTHING R.L SOIL WR/HR
No. drilled

9 VR-9 782800.382 1434738.33 909.25 7.5 19.5 27

10 VR-10 782816.772 1434705.076 908.5 15 13 28

11 VR-12 782821.198 1434744.956 908.94 15 13 28

12 VR-13 782793.877 1434818.922 908.82 19.5 7.5 27

13 VR-14 782819.257 1434794.434 908.92 16.5 10.5 27

14 T(VR-MG)-1 782790.301 1434867.993 908.4 15 12 27

15 T(VR-MG)-2 782811.375 1434867.029 908.34 9.5 16 25.5

16 T(VR-MG)-3 782778.322 1434900.189 908.28 9 18 27

17 T(VR-MG)-4 782802.959 1434901.573 908.1 8.5 18.5 27

18 T(VR-MG)-5 782767.711 1434944.69 907.61 6 21 27

19 T(VR-MG)-6 782790.877 1434943.02 907.73 9 13.5 22.5

20 T(VR-MG)-7 782760.122 1434975.691 907.23 10.5 16.5 27

21 T(VR-MG)-8 782781.561 1434983.646 907.27 13.5 10.5 24

22 T(VR-MG)-9 782753.134 1435001.544 906.97 2.75 24.25 27

23 T(VR-MG)-10 782789.662 1435012.026 906.98 13.5 13.5 27

24 T(VR-MG)-11 782735.873 1435049.043 906.19 21 6 27

25 Tunnel between T(VR-MG)-12 782770.19 1435052.703 906.13 10.5 10.5 21

Vellara Road
26 Station and MG T(VR-MG)-13 782739.187 1435105.138 905.32 24.5 1.5 26
Road Station
27 T(VR-MG)-14 782754.73 1435125.259 904.88 25.5 1.5 27

28 T(VR-MG)-15 782749.198 1435156.467 904.17 18 6 24

29 T(VR-MG)-16 782768.692 1435181.175 903.08 6 19.5 25.5

30 T(VR-MG)-17 782762.502 1435203.249 902.79 15 9 24

31 T(VR-MG)-18 782783.381 1435231.451 901.71 23 0 23

32 T(VR-MG)-19 782776.079 1435246.797 901.51 21.5 1.5 23

33 T(VR-MG)-20 782798.186 1435276.055 900.67 22 0 22

34 T(VR-MG)-21 782787.877 1435286.092 900.54 20.5 1.5 22

35 T(VR-MG)-22 782810.08 1435314.928 900.1 23 0 23

36 T(VR-MG)-23 782798.139 1435317.585 900.2 16.5 4.5 21

37 T(VR-MG)-24 782819.147 1435346.393 900.03 18 3 21

38 T(VR-MG)-25 782809.28 1435352.233 900.02 3 18 21

39 T(VR-MG)-26 782831.409 1435380.577 899.95 9 12 21

40 T(VR-MG)-27 782822.046 1435394.092 899.77 15 6 21

41 Tunnel between T(VR-MG)-28 782842.43 1435436.244 900.44 20 3 23

Vellara Road
42 Station and MG T(VR-MG)-29 782830.401 1435439.453 900.55 20 3 23
Road Station
43 T(VR-MG)-30 782847.872 1435522.137 902.62 23 0 23

44 T(VR-MG)-31 782826.693 1435494.35 901.5 15 8 23

45 T(VR-MG)-32 782855.465 1435552.862 903.58 19.5 5.5 25

For internal use only

Sl. Total depth
Location BH No. EASTING NORTHING R.L SOIL WR/HR
No. drilled

46 T(VR-MG)-34 782868.273 1435594.194 905.3 25.5 1.5 27

47 T(VR-MG)-36 782870.9 1435626.279 906.04 6 24 30

48 T(VR-MG)-37 782868.268 1435660.059 907.3 6 24 30

49 T(VR-MG)-38 782882.382 1435662.383 907.63 6 24 30

50 T(VR-MG)-40 782889.134 1435684.454 908.45 6 24 30

51 T(VR-MG)-42 782894.682 1435703.729 908.62 13.5 16.5 30

52 T(VR-MG)-43 782882.285 1435736.168 909.64 6 24 30

53 T(VR-MG)-44 782899.222 1435719.146 909.06 7.5 22.5 30

54 T(VR-MG)-46 782908.165 1435747.115 909.78 7.5 22.5 30

55 T(VR-MG)-48 782916.069 1435778.781 910.52 6 24 30

56 T(VR-MG)-50 782922.741 1435800.65 911.16 13.5 16.5 30

57 MG-1 782924.173 1435862.506 912.06 30 0 30

58 MG-2 782956.651 1435849.46 911.73 24 7 31

59 MG-3 782932.436 1435891.096 912.36 30 0 30

60 MG-4 782968.934 1435889.845 912.27 30 0 30

61 MG-5 782945.396 1435928.408 912.45 30 0 30

62 MG-6 782981.323 1435931.474 912.83 31 0 31

63 MG Road Station MG-7 782957.784 1435965.254 912.96 31 0 31

64 MG-8 782992.21 1435969.97 913 31 0 31

65 MG-9 782968.675 1435998.769 912.91 31 0 31

66 MG-10 783003.204 1436003.868 913.05 31 0 31

67 MG-11 782979.942 1436031.004 912.95 27 4 31

68 MG-12 783013.106 1436033.466 912.95 21 10 31

69 MG-13 783006.911 1436083.989 912.5 9 22 31

70 MG-14 783024.371 1436074.108 912.54 16.5 14.5 31

71 Tunnel between T(MG-SN)-01 783017.891 1436118.054 911.84 10.5 20.5 31

MG Road Station
72 and Shivajinagar T(MG-SN)-03 783017.471 1436140.553 911.16 10.5 18 28.5

73 Station T(MG-SN)-11 782865.791 1436374.387 908.54 16.5 7.5 24

74 T(MG-SN)-12 782860.697 1436357.771 908.42 12 12 24

75 T(MG-SN)-13 782854.102 1436379.25 908.15 9 15 24

76 T(MG-SN)-14 782847.368 1436361.785 909.13 15 6 21

77 Tunnel between T(MG-SN)-15 782797.393 1436483.667 907.35 22 6 28

MG Road Station
78 and Shivajinagar T(MG-SN)-16 782807.919 1436297.393 911.85 18 7 25
Station
79 T(MG-SN)-17 782693.158 1436477.428 910.04 13.5 14.5 28

80 T(MG-SN)-18 782695.52 1436333.704 912.91 18 10 28

81 T(MG-SN)-19 782659.463 1436525.74 909.27 21 6 27

82 T(MG-SN)-20 782662.572 1436411.295 911.65 24 4 28

For internal use only

Sl. Total depth
Location BH No. EASTING NORTHING R.L SOIL WR/HR
No. drilled

83 T(MG-SN)-21 782596.81 1436543.472 909.49 18 10 28

84 T(MG-SN)-22 782584.738 1436370.233 913.69 28 0 28

85 T(MG-SN)-23 782499.389 1436465.51 912.41 21 7 28

86 T(MG-SN)-24 782501.187 1436402.282 914.45 28 0 28

87 T(MG-SN)-25 782481.946 1436577.554 910.05 28 0 28

88 T(MG-SN)-26 782488.175 1436431.892 913.63 18 10 28

89 T(MG-SN)-27 782455.047 1436585.166 910.79 28 0 28

90 T(MG-SN)-28 782443.77 1436420.718 914.68 15 13 28

91 T(MG-SN)-29 782437.326 1436582.866 911.75 28 0 28

92 T(MG-SN)-30 782404.336 1436433.726 914.87 27 0 27

93 T(MG-SN)-32 782456.277 1436574.731 912.08 27 0 27

94 T(MG-SN)-39 782383.77 1436624.935 911.07 27 0 27

95 T(MG-SN)-40 782385.794 1436634.969 910.75 28 0 28

96 T(MG-SN)-41 782388.556 1436646.323 910.6 25.5 2.5 28

97 SN-A 782379.36 1436522.282 912 21 9 30

98 SN-1 782387.685 1436672.219 909.39 18 9 27

99 SN -2 782361.909 1436680.921 908.96 15.5 11.5 27

100 SN -3 782341.683 1436689.213 909.04 18 8.5 26.5

101 SN -4 782335.105 1436695.817 908.91 22.5 4.5 27

102 Shivajinagar SN -5 782304.625 1436721.121 908.11 30 0 30

Station
103 SN -6 782309.512 1436739.642 908.15 27 0 27

104 SN-6A 782278.48 1436711.304 908.21 28 0 28

105 SN -7 782289.23 1436739.919 908.16 25.5 4.5 30

106 SN -8 782297.668 1436770.182 908.12 24 3 27

107 SN -9 782278.247 1436755.303 908.16 30 0 30

108 SN -10 782289.415 1436793.532 908.04 27 0 27

109 SN-10A 782251.855 1436751.963 908.28 28 0 28

110 SN -11 782266.668 1436784.841 908.13 28 0 28

111 SN -12 782260.524 1436806.263 908.21 27 0 27

Shivajinagar
112 Station SN -13 782282.885 1436811.214 908.01 27 0 27

113 SN -13A 782245.444 1436843.384 911.93 28 0 28

114 SN -14 782266.437 1436820.618 908.16 27 0 27

115 SN-15 782223.838 1436828.315 907.1 30 0 30

116 T(SN-CM)-2 782196.353 1436873.345 906.5 22.5 7.5 30

Tunnel between
117 Shivajinagar T(SN-CM)-3 782172.94 1436909.279 905.41 19.5 6.5 26

118 Station and T(SN-CM)-4 782161.247 1436902.563 905.68 18.5 7.5 26

Cantonment
119 T(SN-CM)-5 782155.338 1436927.486 905.13 27 0 27

For internal use only

Sl. Total depth
Location BH No. EASTING NORTHING R.L SOIL WR/HR
No. drilled

Station
120 T(SN-CM)-6 782151.952 1436915.252 905.54 27 0 27

121 T(SN-CM)-7 782150.203 1436958.838 903.53 21 4 25

122 T(SN-CM)-8 782132.935 1436943.702 904.55 21 4 25

123 T(SN-CM)-9 782123.329 1436969.389 903.93 9 16 25

124 T(SN-CM)-10 782121.575 1436949.961 904.62 12 13 25

125 T(SN-CM)-11 782130.235 1436981.607 903.06 7.5 17.5 25

126 T(SN-CM)-12 782082.054 1436979.794 904.4 18 7.5 25.5

127 T(SN-CM)-13 782104.617 1437035.592 902.19 9 16 25

128 T(SN-CM)-14 782091.474 1436996.394 903.72 7.5 17.5 25

129 T(SN-CM)-15 782090.432 1437036.895 902.72 7.5 17.5 25

130 T(SN-CM)-16 782067.157 1437018.708 903.92 9 16 25

131 T(SN-CM)-17 782057.414 1437066.704 903.98 13.5 7.5 21

132 T(SN-CM)-19 782032.855 1437075.935 904.4 13 12 25

133 T(SN-CM)-21 781986.241 1437085.202 904.62 13.5 3 16.5

134 T(SN-CM)-22 782003.15 1437126.402 903.57 9 7.5 16.5

135 T(SN-CM)-23 781978.76 1437141.996 903.6 6 18 24

136 T(SN-CM)-24 781956.096 1437156.388 903.79 5.5 17.5 23

137 T(SN-CM)-25 781939.703 1437167.151 904 4.5 13.5 18

138 T(SN-CM)-26 781964.011 1437184.032 902.75 6 9.5 15.5

139 T(SN-CM)-27 781925.5 1437176.376 904.21 12 4.5 16.5

140 T(SN-CM)-28 781912.488 1437196.318 904.28 9 13.5 22.5

141 T(SN-CM)-29 781920.421 1437214.788 903.71 12 7 19

142 T(SN-CM)-31 781904.178 1437214.077 908.95 16.5 1.5 18

143 T(SN-CM)-32 781891 1437228.575 909.02 12 8 20

144 T(SN-CM)-33 781884.701 1437210.659 908.96 12 6 18

145 T(SN-CM)-34 781840.841 1437243.89 906.29 12 6 18

146 T(SN-CM)-35 781843.24 1437265.037 906.27 10.5 9 19.5

147 T(SN-CM)-36 781827.662 1437263.534 906.45 10.5 10.5 21

148 T(SN-CM)-37 781833.484 1437283.495 906.04 12 9 21

Tunnel between
149 Shivajinagar T(SN-CM)-38 781811.012 1437282.768 906.19 4.5 18 22.5
Station and
150 T(SN-CM)-39 781813.832 1437305.403 906.16 7.5 13.5 21
Cantonment
151 Station T(SN-CM)-40 781796.228 1437302.642 906.2 6 12 18

152 T(SN-CM)-41 781803.195 1437321.491 906.17 8 13 21

153 T(SN-CM)-42 781785.085 1437322.046 906.28 6 15 21

154 T(SN-CM)-43 781786.115 1437340.721 906.15 9 12 21

155 T(SN-CM)-45 781764.441 1437379.646 905.55 4 14 18

156 T(SN-CM)-47 781769.345 1437495.024 909.03 1.7 20.3 22

For internal use only

 Sl. Total depth
Location BH No. EASTING NORTHING R.L SOIL WR/HR
No. drilled

157 T(SN-CM)-48 781744.518 1437520.728 909.27 3.5 21.5 25

158 T(SN-CM)-49 781771.211 1437509.798 909.37 3 27 30

159 T(SN-CM)-50 781758.405 1437526.61 909.76 3.5 26.5 30

*HR - Hard Rock, SR – Soft rock, SDR – Soft Disintegrated Rock. The classification given in the factual
geotechnical report is reproduced here as is. There is no specific code that classifies rock in this fashion.

5.1.2 Laboratory and Field Test

The following table shows a summary of field and laboratory tests done.
Table 5 : Existing Information: Field and Laboratory Testing

GI Type Item Remarks

SPT Yes
Permeability Testing in Soil Yes
Permeability Testing in Rock Yes
Fieldwork Piezometer monitoring of
Yes
Groundwater
Pressuremeter Test No
Core Box Photograph Yes
Natural Moisture Content Yes
Atterberg Limits Yes
Grain Size Distribution Yes
Bulk Density Yes
Laboratory Testing on Triaxial Testing Yes
Soil Direct Shear Box Testing Yes
Unconfined Compression Test Yes
Consolidation Test Yes
Specific Gravity Yes
Free Swelling No
pH Yes
Chemical Testing on soil
& Water Chloride (ppm) Yes
Sulphate (ppm) Yes
Core Recovery & RQD (%) Yes
Bulk Density Yes
Water absorption (%) Yes
Laboratory Testing on
Rock Natural Moisture No
Specific gravity Yes
Porosity (%) Yes
Uniaxial Compressive Strength Yes

For internal use only

 GI Type Item Remarks
Point load strength Yes
Modulus of Elasticity Yes
Hardness Yes
Brazilian Tensile Strength No
Petrographic Analysis No

6. Results

This section contains the interpretation of test results and derivation of design parameters. The
geotechnical parameters described in the sections below are derived based on available data from
the investigation reports.

The methodology followed to arrive at the geotechnical parameters is as follows:

 The field/laboratory test results are analyzed to study the general characteristics of the sub
soil layers. This is discussed in Sections 6.1 and 6.2.
 The range of geotechnical parameters is taken corresponding to the values obtained from
the laboratory test results. This is discussed in Section 6.2.

Design parameters for this package are based on the information available from lab test and
literature as described in the followings sections.

6.1 Laboratory Test Results

Summary of laboratory test results are given in the following sections.

6.1.1 Grain Size Distribution

The grain size distribution along the alignment indicates predominantly silty sand. In some areas
clayey silt layers with low compressibility are also observed. Detailed summary of grain size
distribution results are provided in the Geotechnical investigation reports.

6.1.2 Natural Moisture Content

Natural moisture content varies from 9% to 25% for soils.

6.1.3 Atterberg Limits

Vast majority of samples scheduled for Atterberg Limits were deemed to be “Low to High Plastic”.
Plasticity Index values range from approximately 5% to 39% and Liquid Limit generally ranges from
25% to 70% indicating the material to be mainly sandy silt & clayey silt with low to high plasticity.

For internal use only

6.1.4 Bulk Density

The bulk density for sandy silt / silty sand varies between 17.0 to 20.5 kN/m3 based on laboratory
test results. Since the values depend on degree of disturbance, the values are compared with the
range available in literature and appropriate values are picked for specific type of soil. The bulk
densities of the soil layers are taken in accordance with BS 8002:1994. This is discussed in section
7.1.2.

6.1.5 Triaxial Testing

Triaxial tests were conducted on cohesive soil samples. However, the results were not consistent
and hence have not been used for deriving the design parameters. The strength parameters are
adopted based on empirical correlations with SPT ‘N’ values. This is discussed in Section 6.2.

6.1.6 Chemical Aggressivity and Corrosion

Design of underground structures will be carried out in accordance with relevant Standards on
resistance to attack by ingress of sulphate and chloride.

Chemical analyses of soil-water extracted samples indicate that the pH value of water is in the
range of 4.16 to 8.48, sulphate content is in the range of (0.001 to 0.025 % by mass) 10 to 250 mg/l
and chloride content is in the range of (0.0016 to 0.058% by mass) 16 to 580 mg/l. The soil and
ground water is observed to be non-aggressive based on the lab test results. This is discussed in
Section 7.3.

6.1.7 Tests on Rock

The rock type encountered is mostly granitic gneiss along the alignment. Plots of RQD vs depth and
UCS of intact rock vs depth for all the rock samples are presented in

Appendix – B.
6.2 Field Test Results

6.2.1 SPT ‘N’ Distribution

Charts given in the Appendix – A show the distribution of field (uncorrected) SPT ‘N’ value with
depth for the soil types encountered along the specific stretches of the alignment. As per the plot,
2 to 4m of soil below ground level has SPT ‘N’ value ranging from 15 to 20. Below this depth, the
average SPT ‘N’ values increase with depth until refusal (>100) is observed on top of rock.

According to CIRIA Report 143 Table-9, as produced below, SPT values corrected to overburden
(N1) and 60% (N60) of theoretical free-fall hammer energy is used in determining the drained friction
angle of sands. In order to determine undrained cohesion, Elastic modulus of cohesive soils and
drained elastic modulus of granular soils, SPT values corrected to 60% of theoretical free-fall

For internal use only

hammer energy are used. Since IS 6403 does not mention N60, the field SPT value is considered as
N60 value.
The bore logs for each stretch of the alignment are studied to arrive at the soil profile and
consistency of soil based on SPT ‘N’ Values. Design parameters for the considered stretch of the
alignment are derived based on the corrected SPT ‘N’ Values as per CIRIA Report 143 table 9 as
shown below.

Table 6 : Determination of Parameters from SPT Values (CIRIA Report 143)

Material Type Required

Parameter
Granular Soil Cohesive Soil Weak Rock Chalk Input
∅’ * (N1)60
Cu * * N60
σc * * N60
Eu * N60
E’ * * * * N60
mv * N60
Gmax * (N1)60
Note: N1 is SPT N value corrected to 100 kPa effective overburden pressure
N60 is SPT N value corrected to 60% of theoretical free-fall hammer energy
(N1)60 is SPT N value corrected for both vertical effective stress and input energy

Overburden correction factor can be calculated by using graph presented in CIRIA Report 143 (Fig.
28) and IS 2131 (Fig.1). Overburden correction factor is only required for deriving effective friction
angle (CIRIA 143) for cohesion less soils.

6.2.2 Permeability Test Results

Field permeability tests were carried out to determine the permeability of soil. Based on the field
test results average permeability values for the different soil layers are summarized in the Table 7
below and the plot of test results with depth is presented in Appendix-A.
Table 7 : Permeability values for soil layers based on Test Results

Range of Coefficient of Design Coefficient of

Soil Type
Permeability (cm/sec) Permeability (cm/sec)

Sandy SILT/Silty SAND 0.11E-05 to 5.51E-05 1.69E-05

7. Geotechnical Assessment

Laboratory test results are interpreted in Section 6.1 and 6.2. Accordingly the parameters for
different layers are aimed to be derived, based on the lab test results. However, the results are
found to be inconsistent and also there is lack of data at deeper depths. Therefore, the parameters
are derived from the SPT ‘N’ values based on empirical relationships. Interpretation of these
parameters is discussed in this section.

For internal use only

7.1 Soil Parameters

7.1.1 Consistency based on SPT Values

CIRIA Report recommends the procedure for determining the consistency of soil based on SPT ‘N’
values. The Chart given by CIRIA Report (Table-8) is reproduced below.

Table 8 : Consistency based on SPT values from CIRIA Report 143

SPT N Values
SPT (N1)60 Values Consistency
(Uncorrected)
For Cohesion less Soils
0-4 0-3 Very loose
4-10 3-8 Loose
10-30 8-25 Medium
30-50 25-42 Dense
>50 >42 Very Dense
For Cohesive Soils
0-4 - Very Soft
4-8 - Soft
8-15 - Firm
15-30 - Stiff
30-60 - Very Stiff

>60 - Hard

7.1.2 Bulk Density

The bulk densities of the soil layers are taken in accordance with BS 8002:1994 (Table-1).

Table 9 : Unit Weight of Soil according to BS 8002: 1994

Bulk Density, γb (kN/m3) Saturated Density, γsat (kN/m3)

Material
Loose Dense Loose Dense

Granular Soils

Gravel 16 18 20 21

Well graded sand and

19 21 21.5 23
gravel

Coarse or medium sand 16.6 18.5 20 21.5

For internal use only

 Bulk Density, γb (kN/m3) Saturated Density, γsat (kN/m3)
Material
Loose Dense Loose Dense

Well graded sand 18 21 20.5 22.5

Fine or silty sand 17 19 20 21.5

Rock Fill 15 17 19.5 21

Brick hard core 13 17.5 16.5 19

Slag fill 12 15 18 20

Ash Fill 6.5 10 13 15

Cohesive Soils

Peat (very variable) 12 12

Organic Clay 15 15

Soft Clay 17 17

Firm Clay 18 18

Stiff Clay 19 19

Hard Clay 20 20

Stiff or Hard Glacial clay 21 21

7.1.3 Permeability

In places where field/lab permeability tests are not available, it is possible to estimate approximate
values of “coefficient of permeability “ for soils as published in the FHWA manual, which is
reproduced below for easy reference.

Table 10 : Range of Permeability values for different soils (FHWA)

Coefficient of
Drainage Soil Type
Permeability (cm/sec)

102 – 1 Very Good Drainage Gravel

1 – 10-4 Good Clean Sand and Gravel-Sand Mixture

Very Fine Sand, Organic and Inorganic Silts

10-4 – 10-6 Poor
and Mixture of Sand, Silt and Clays

10-6 – 10-9 Practically Impervious Clay

For internal use only

7.1.4 Strength and Stiffness Parameters

7.1.4.1 Undrained Behavior

The soil that exhibits undrained behavior during excavation is assumed to have low permeability.
Clay and silt fall in this category.

Undrained shear strength (Cu) values is conservatively estimated, based on corrected SPT values
(N60) as per CIRIA Report 143.

Cu=5*N60 (kPa).............................................................................................Eqn 1

Where, N60 is field SPT ‘N’ value.

The same are also reflected in other references as given in Table 11 below where Undrained Shear
Strength is Cu=0.5*qu. The value of qu is approximately qu =12*N60.

Table 11 : Relationship between compressive strength and SPT Value and consistency of
saturated Cohesive Soils (from Terzaghi & Peck, 1967)

Consistency N60 qu, (kPa) Remarks

Very Soft <2 <25 Squishes between fingers when squeezed

Soft 2-4 25-50 Very easily deformed by squeezing

Medium 4-8 50-100 -

Stiff 8-15 100-200 Hard to deform by Hand squeezing

Very Stiff 15-30 200-400 Very hard to deform by Hand squeezing

Hard >30 >400 Nearly Impossible to deform by hand

Undrained secant (elastic) modulus Eu is assumed to be based on corrected SPT value Correlation
as given below.
Eu=1.2*N60 (MPa)..............................................................Eqn 2 (CIRIA Report 143)

The undrained Poisson’s Ratio (μu) for total stress analysis is 0.5. In finite element analysis the value
to be used is 0.495 to avoid numerical instability. Values of Poisson’s ratio can be obtained from the
table below:

Table 12 : Value Ranges for Poisson’s Ratio (from Bowels-Fifth edition)

Soil Type μ, Ranges

Clay, Saturated 0.4-0.5

Clay, Unsaturated 0.1-0.3

Silt 0.3-0.35

For internal use only

 Sand, Commonly used 0.3-0.4

Rock 0.1-0.4
The coefficient of earth pressure at rest K o is estimated using the equation Ko= (1-sinφ’)

7.1.4.2 Drained Behavior

Sand layers are considered as Cohesion less drained material.

 The effective cohesion (c’) is assumed to be 10 kPa because of presence of small
proportions of silt and clay.
 Angle of internal friction (Φ’) value for sands are obtained from SPT values as suggested in
IS: 6403-1981 and is given below. Overburden correction is applied before choosing the
friction angle from the chart.

Figure 2: Relationship between Φ and SPT N Value (IS: 6403 – 1981)

 For Clayey and Silty Sand, the value of friction angle obtained from Figure 5 is reduced
by 5 degrees (IS 6403:1981).
 The effective Poisson’s ratio μ’ is assumed to be 0.3 (from
 Table 12).
 The drained modulus E’ is computed based on correlation given in CIRIA Report 143.
For Clayey and Silty sand, E’ = 1.0*N60…………………………………Eqn 3
For Silt and Clay of medium to High Compressibility, E’ = 0.7*N60…..Eqn 4

The generalized values of design parameters for a particular type and consistency of soil/rock
encountered along the alignment are described in the following sections.

For internal use only

7.2 Geotechnical Design Parameters for Soil

Geotechnical Design parameters are summarized in section 8.4. Values of SPT (N1)60 are only used
to calculate effective angle of internal friction for cohesion less soils.

7.3 Chemical Aggressivity and Corrosion – Soil and Groundwater

Design of underground structures will be carried out in accordance with relevant Standards on
resistance to attack by ingress of sulphate and chloride.

The test results available to estimate the chemical aggressiveness of ground water and soil
indicate that both the soil and ground water are non-aggressive in nature.
Allowable limits of Chemical analysis of water are summarized in Table 13 to Table 15. In the current
case pH ranges from neutral to moderately alkaline. Chloride content is observed to be negligible
and sulphate content also falls under Class 1 which is considered negligible. Hence the soil and
ground water is generally non-aggressive in nature and no special care will be needed to prevent
corrosion. The table below shows the different categories of corrosiveness of chlorides and
sulphates in soil and ground water on concrete, as given in IS: 456.

Table 13 : Classification based on Sulphates in soil and ground water as per IS: 456

Concentration of Sulphates, expressed as SO3

Class In Groundwater (mg/l)
In-Soil-Water Extract (Total) Percent
1 Traces ( <0.2) Less than 300

2 0.2 to 0.5 300-1200

3 0.5 to 1 1200-2500

4 1 to 2 2500-5000

5 >2 >5000

Table 14 : Classification based on Chlorides content as per IS: 456

Chloride Limits
Classification
Temperate Climate Tropical Climate

Negligible 0-2000 ppm Not applicable

Moderate 2000-10000 ppm 0-2000 ppm

High More than 10000 2000-20000 ppm

Very High Generally not applicable If only considerably in excess of 20,000 ppm

Table 15 : Classification based on PH values

Classification pH
Extremely acid < 4.5

For internal use only

 Classification pH
Very strongly acid 4.5 – 5.0
Strongly acid 5.1 – 5.5
Moderately acid 5.6 – 6.0
Slightly acid 6.1 – 6.5
Neutral 6.6 – 7.3
Slightly alkaline 7.4 – 7.8
Moderately alkaline 7.9 – 8.4
Strongly alkaline 8.5 – 9.0
Very strongly alkaline >9.1

The soil and ground water are not aggressive as indicated by the chemical analyses. Hence no
special care needs to be taken for concrete.

7.4 Rock Parameters

Based on the Geotechnical assessment, Contract package T-104 has overburden soil followed by
rock. The rock type encountered along the stretch is predominantly Granitic Gneiss.

7.4.1 Classification of Rock

Classification of rock based on weathering grades is suggested in IS 4464. This is based on visual
observation of weathering of the rock and is more qualitative. The classification of rock based on
weathering grades (IS 4464) is presented in Table 16.
Table 16 : Classification of rock based on weathering grades (IS 4464)

Weathering class Description of rock material and rock

Strength
and grade Mass

No visible sign of material weathering. Near

Fresh (I) Boundary with Grade II some slight Very High
discoloration on major defects
Discoloration indicates weathering of rock
Slightly weathered material and defect surface. Discoloration Very high to 50-60% of
(II) ranges from defect surface only to fresh rock strength
completely stained
Less than 50 % material decomposed and
Moderately 30% of fresh rock
disintegrated to intact soil. Rock core
weathered (III) strength
discoloured and weakened.
More than 50 % material decomposed and
15% of fresh rock
Highly weathered (IV) disintegrated to intact soil. Rock core
strength
discoloured and weakened.
Completely Intact friable soil which may be weakly
Extremely low
weathered (V) cohesive. Soil has fabric of parent rock.

Residual soil (VI) Friable soil with original rock fabric Extremely low

For internal use only

 Weathering class Description of rock material and rock
Strength
and grade Mass

completely destroyed

Since the above classification system is qualitative, it was thought of bringing in a quantitative
approach to classification. In Chennai Metro, to have a quantitative approach to the classification,
Core Recovery (CR) and Rock Quality Designation (RQD) were introduced. For the Mumbai Metro
Line 3 a similar classification was adopted. Table 17 below shows the classification of weathering
grades followed in Chennai and Mumbai Metros.
Table 17 : Classification of weathering grades based on CR and RQD

Index Properties
Weathering class Description of rock Effective
Strength CR RQD
and grade material and rock Mass Porosity
[%] [%]

No visible sign of material

weathering. Near
95-
Fresh (I) Boundary with Grade II Very High 90-100 -
100
some slight discoloration
on major defects
Discoloration indicates
weathering of rock Very high
material and defect to 50-60% 5% increase
Slightly
surface. Discoloration of fresh 90-95 75-90 from fresh
weathered (II)
ranges from defect rock rock
surface only to strength
completely stained
Less than 50 % material
decomposed and
30% of
Moderately disintegrated to intact
fresh rock 60-90 40-75 7% increase
weathered (III) soil. Rock core
strength
discoloured and
weakened.
More than 50 % material
decomposed and
15% of
Highly weathered disintegrated to intact
fresh rock 30-60 10-40 10% increase
(IV) soil. Rock core
strength
discoloured and
weakened.
Intact friable soil which
Completely may be weakly cohesive. Extremely
0-30 0-10 20% increase
weathered (V) Soil has fabric of parent low
rock.
Friable soil with original
Extremely
Residual soil (VI) rock fabric completely 0 0 >20 %
low
destroyed

For internal use only

On inspecting the core logs, and subsequent discussions with BMRCL geologist with due
consideration to the experience gained from Phase 1, it was felt that the classification mentioned in
Table 17 would not be suitable for Bangalore Geology and a separate site specific classification
system would have to be developed. It was felt that while this classification should be simple, it
should be robust enough to be able to capture the complexity of the geological features and
address the tunneling issues faced in Phase 1.

Considering the variability of the rock types, the weathering grades, the structural patterns like
jointing and foliations, and the strength of the intact rock along the alignment it was decided to
have a site specific classification system based on RQD alone. It may be noted that the geology of
Bangalore is far more complex and varied compared to Chennai or Mumbai.

The rock classification suggested for Bangalore Metro Reach 6 is given in Table 18. And a plot of
RQD vs Depth for rock strata is given in

Appendix – B.
Table 18 : Classification of weathering grades based on RQD

Grade Rock Type RQD

II Slightly Weathered 60 to100

III Moderately weathered 30 to 60

IV/V Highly weathered/ completely weathered <30

7.4.2 UCS Test Results of Rock

The unconfined compressive strength test was carried out on selected rock core samples. A plot of
the UCS of intact rock vs Depth for rock based on weathering grade is given in

Appendix – B.
Average UCS values are summarized in Table 19 below.

Table 19 : Average UCS (Intact Rock) Test Results

Sl. No. Package Rock Type Weathering Grade UCS, MPa

1 II 75
2 T-104 Granitic Gneiss III 60
3 IV/V 30

For internal use only

7.4.3 Point Load Strength Index Test Results of Rock

Point load tests were carried out on select intact rock core samples as per IS 8764. Although the
point load test is an index test for rock, it has been equated with the unconfined uniaxial
compressive strength. The Uniaxial compressive strength of rock predicted from the following
equation as given in IS 8764.

UCS = 22*Is(50)………………………………………………………………………...Eqn 5

Where,
Is(50) is corrected point load strength.
The average Is(50) values are presented in

Table 20

Table 20 : Average Is(50) Test Results

Is(50) converted to UCS,

Sl. No. Weathering Grade Is(50) (MPa)
MPa (22*Is(50)

1 II 2 44.0
2 III 1.7 37.4
3 IV/V 1.2 26.4
The average UCS values obtained from Laboratory test results are compared with the empirically
calculated UCS values from Point Load Strength Index for Rock. Since higher values are observed,
no correlation between the two tests is established. Plots of the (Is) vs Depth are given in

Appendix – B.
7.4.4 Rock Mass Rating System (Bieniawski)

The Geomechanics classification or the Rock Mass Rating (RMR) system was initially developed at
the South African Council of Scientific and Industrial Research by Bieniawski (1973) on the basis of
his experience in shallow tunnels. This was further revised in 1989. The classification parameters
and ratings are reproduced in Appendix-D. IS:13365-(Part1)-1998 and further amended in 2008
gives guidelines for estimation of RMR.

For this project, the RMR classification has been carried out purely based on visual inspection of
available corelogs. Hence the parameters confirming discontinuities i.e. spacing, condition and
orientation are based on the reference given in Appendix-D and engineering judgement. This may
vary during the actual excavation of the tunnel.

RMR values and its correlation with the weathering grades are presented in the Table 21.

For internal use only

 Table 21 : Rock Mass Classification based on RMR (IS :13365 (Part 1)-1998)
Adjustment for
Spacing of Condition of Discontinuity
UCS RQD Ground water
discontinuities discontinuities orientations for Total
Weathering Rock
Tunnels Rating Description
Grade Class
(RMR)
[MN/m²] Rating [%] Rating m Rating Description Rating Description Rating Condition Rating

Separation
<1mm slightly
Grade II 75 7 >60 13 0.6-2 15 25 Damp 10 Unfavorable -10 60 III Fair Rock
weathered
walls
Separation
<1mm Highly
Grade III 60 7 30-60 8 0.2 - 0.6 10 20 Wet 7 Unfavorable -10 42 III Fair Rock
weathered
walls
Separation 1-
Very Poor
Grade IV/V 30 4 <30 3 <0.06 5 5 mm 10 Dipping 4 Unfavorable -10 16 V
Rock
continuous

7.4.5 Geological Strength Index (GSI)

Hoek and Brown (1997) introduced the Geological Strength Index (GSI), both for hard and weak rock masses. GSI value is derived from a chart that
classifies rock mass on the basis of visual inspection of geological condition presented in Table 22. This classification is incorporated in IS:13365 (Part 4)
which is in draft stage.
 Table 22 : Representative values of GSI for different rock grade (IS 13365 Part 4)

GSI value is also calculated based on following equation provided by Bieniawski (1989).

GSI = RMR-5…………………………………………………………………………...Eqn 6

The GSI values for the rock mass are presented in Table 23.

Table 23 : Rock mass classification

 Weathering
Rock Type RMR GSI
Grade
II 60 55

III Granitic Gneiss 42 37

IV/V 16 11

7.4.6 Deformation Modulus of Rock Mass

An estimation of deformation modulus (E m) of the rock mass can be obtained using GSI using the
relationship published by Hoek (2002).

The rock mass modulus of deformation is given by-

………………………Eqn 7

Where,
D is disturbance factor (D=0, for TBM as described in the paper. D is also defined in IS 13365
(Part 4)
σci is Uniaxial Compressive Strength of intact rock, MPa
GSI is Geological Strength Index

The Deformation Modulus of rock mass for the different grades derived from Eqn 7 is presented in
Table 24.

Table 24 : Stiffness Parameters of Rock

Deformation Modulus, Em
Rock Class Rock Type σci, MPa GSI
(Hoek), GPa

II 75 55 11.55
Granitic
III 60 37 3.67
Gneiss
IV/V 30 11 0.58

Elastic modulii of intact rock obtained from lab test are also presented in Appendix-B.

7.4.7 Lugeon Test

Packer test also known as Lugeon test is a water pressure test, where a section of the drill hole is
isolated and water is pumped into that section until the flow rate is constant. Single packer
permeability tests are used in this project. A Lugeon is defined as the water loss of 1
liter/minute/length of test section at an effective pressure of 1 MPa. 1 Lugeon is approximately
equal to 10-7 m/s.

The plot of Permeability vs Depth obtained through tests is presented in

Appendix – B with values varying from 0.01 to 7.18 Lugeons.
Table 25 shown below gives a relationship between Lugeon and the joint condition. For the present
alignment, the joint condition varies from small joint openings to closed or no joints. Some open
joints are also present at vellara road station.
Table 25 : Indicative rock permeability’s (Look 2007)

8. Conclusion and Recommendations

8.1 Groundwater Conditions

Water level observations during drilling of boreholes in the GI indicate ground water table ranging
from 10 to 16m depth below the ground level along the alignment except at shivajinagar station
where water level found to be at 6m below ground level.

In order to provide information on the seasonal variation, during construction phase, monitoring
shall be carried out in standpipe/piezometer installed at the shaft and station locations. It is
recommended to maintain water level monitoring installations during the site construction
activities.

8.2 In-situ Conditions

Geotechnical assessment along the alignment is carried out in above sections. This stretch has soil
followed by rock strata at few locations continuous soil is encountered up to termination depth.

The soil deposit is predominantly silty sand & sandy silt of low plasticity. For the soil type in the
stretch, the available data indicate that the strength and stiffness parameters can be correlated to
SPT ‘N’ blow count.

The rock type is predominantly granitic gneiss observed throughout the stretch.

8.3 Settlement Predictions

As per the available ground investigation results, the running tunnel within this package will
generally be embedded in rock of Grade III or higher with anticipated minimum rock cover of about
1.3m. At some locations, tunneling in mixed ground to soft ground is anticipated. This has to be
considered while calculating the volume loss and settlement prediction.
8.4 Design Parameters

Design parameters for soil and rock are derived from the plots presented in Appendix 1 and 2. Codes do not specify any guideline for the derivation of
design parameters, while it emphasizes on engineering judgement.
Table 26 : Generalized Design Parameters for Soil

Field SPT ‘N’ design

Undrained Parameters Drained Parameters

Field SPT ‘N60’

Strength Stiffness Strength Stiffness

line (N60)

Values
Detailed Parameters Parameters Parameters Parameters
Location
Description
cu u Eu c’ * ’ ^E’
μu μ'
kPa deg MPa kPa deg MPa

Vellara Road station Sandy SILT N = 18 + 5z (4<z<18) 18-88 - - - - 10 31-38 18-88 0.3
Tunnel between Vellara road
Sandy SILT N = 20 + 5z (4<z<12) 20-60 - - - - 10 32-36 20-60 0.3
and MG road stations
Sandy SILT
MG Road station N =12 + 4z (5<z<18) 12-64 - - - - 10 28-36 12-64 0.3

Tunnel between MG road and Sandy SILT

N = 15+ 2.2z (4<z<24) 15-59 - - - - 10 30-36 15-59 0.3
Shivajinagar stations
Sandy SILT
Shivajinagar station N = 15 + 3.5z (4<z<22) 15-78 - - - - 10 30-37 15-78 0.3

Tunnel between Shivajinagar Sandy SILT

N = 17 + 5z (4<z<16) 17-77 - - - - 10 31-37 17-77 0.3
and Cantonment stations
N60 - Design line obtained from Appendix-A; * ’ - Values obtained from IS: 6403 derived from SPT N values; ^ E’ - Values derived from Eqn 3;
μ' - Refer table 12
Since there is large scatter in the SPT N values, the design line for N values are based on a 75
percentile line, which means that 75% of all the data points lie above the design line and only 25%
points fall below the line. This line thus represents a situation which is greater than the lower bound
but lesser than the average (50% line).

Table 26 summarizes the generalized design parameters for soil, for design of geotechnical works.
This is based on explanations provided in the previous section.

Table 27summarizes the proposed design parameters for rock

Table 27 : Design Parameters for Rockmass

Deformatio
Rock Class
Rock Type

Rock, MPa

n Modulus
Lugeon

Em, GPa
UCS of
Grade

Intact

value
RMR

GSI
i ii iii iv v vi vii viii
II 75 60 III 55 0.5 11.55
Granitic
III Gneiss 60 42 III 37 1.5 3.67

IV/V 30 16 V 11 2.5 0.58

iii – values derived from Appendix-B; iv – Refer Table 21;

v – Refer Table 21; vi - values derived from Eqn 6;
vii - values derived from Appendix-B; viii - values derived from Eqn 7;

It shall be noted that all design parameters are derived from the factual geotechnical data available
in 2014 with BMRCL as presented in Table 3 . Further, engineering judgement is exercised in
deriving the parameters. These parameters shall be cross verified by the contractor/DDC before
using them for detailed design.
Appendix – A
Plots for Soil
A1. SPT vs Depth
A2. Coefficient of permeability vs Depth

Coefficient of Permeability,K (x 10-5 cm/sec)

0 1 2 3 4 5 6
0

4
Depth (m)

10

12

14
Appendix – B
Plots for Rock
B1. RQD vs Depth
B2. UCS of intact rock vs Depth
B3. Point load index vs Depth
B4. Elastic Modulus of intact rock vs Depth

B5. Coefficient of Permeability vs Depth

Coefficient of Permeability, K in Rock (Lugeon)

0 1 2 3 4 5 6 7 8
0

8
Depth (m)

12

16

20

24

28

32
 Appendix – C
Geological Plan & Profile
 Appendix – D
Geomechanics Classification (Rock Mass Rating)