TUN 1

Report for Karwar Tunnel Noble Geo-Structs Project No. S 16029August 31, 2015

PROJECT DESCRIPTION: ...................................................................................................... 2

SCOPE OF WORK: ................................................................................................................. 3

L-SECTION OF TUNNEL: ....................................................................................................... 3

4

4

GEOLOGY OF KARWAR: ....................................................................................................... 5

GEOTECHNICAL APPRAISAL: .............................................................................................. 9

COMMENTS ON THE QUALITY OF THE ROCK: ................................................................ 12

COMPARISION OF DESIGN PARAMETERS: ..................................................................... 12

FINITE ELEMENT ANALYSIS: ............................................................................................. 14

PLAXIS ANALYSIS: .............................................................................................................. 15

ANALYSIS AND REVIEW OF DESIGN OF TEMPORARY LINER COMPONENTS: .......... 18

SUPPORT SYSTEM ANALYSIS: .......................................................................................... 18

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PROS AND CONS OF PROVISION: ..................................................................................... 20

CONSTRUCTION METHODOLOGY: .................................................................................... 22

ADEQUACY OF TUNNEL SUPPORT: .................................................................................. 23

EXECUTIVE SUMMARY: ...................................................................................................... 24

APPENDIX I CORE LOGS .................................................................................................... 27

APPENDIX II .......................................................................................................................... 29

2


PEER REVIEW OF TUNNEL DESIGN REPORT OF NH 17 KM 93 TO KM 283.300

INTRODUCTION:

PreambleThe twin tube tunnels at Karwar are proposed under 4 laning of Goa/Karnataka Border –

Kundapur section of NH 17 Project. The proposal reduces the length of highway from 4 km

to 2 km with tunnels. The tube tunnels provide a clear minimum width of 8.5m and minimum

vertical clearance of 5.5m. The overall width is 11.5 m. The clear distance between tunnels

is 20m. The alignment is straight having longitudinal gradient of 0.5%.

PROJECT DESCRIPTION:

The details of Tunnels are tabulated below: Figures in parenthesis represent tender stage

considerations.

Table Approximate chainages and lengths of proposed Tunnel 1

Sr. No. DescriptionEast

Tube

Length

(m)

West

Tube

Length

(m)

Total

Length (m)

Starting

Chainage

km

Ending

Chainage

km

Starting

Chainage

km

Ending

Chainage

km

1 Tunnel 1107.000

(106.985)

107.223

(107.185)

223

(200)

106.990

(106.962)

107.209

(107.196)

219

(234)

442

(434)

2 Tunnel 2107.483

(107.470)

107.815

(107.820)

332

(350)

107.490

(107.465)

107.804

(107.825)

314

(360)

646

(710)

Total

Length

1088

(1144)

Table Approximate chainages and lengths of proposed tunnel 2

Sr. No. DescriptionEast

Tube

Length

(m)

West

Tube

Length

(m)

Total

Length (m)

3


Starting

Chainage

km

Ending

Chainage

km

Starting

Chainage

km

Ending

Chainage

km

1 Tunnel 1106.991

(106.985)

107.223

(107.185)

232

(200)

106.980

(106.962)

107.209

(107.196)

229

(234)

461

(434)

2 Tunnel 2107.483

(107.470)

107.815

(107.820)

332

(350)

107.490

(107.465)

107.804

(107.825)

314

(360)

646

(710)

Total

Length

1076

(1144)

Detailed soil investigation is conducted by M/s Soil Tech India Pvt. Ltd. taking boreholes. In

all 3 boreholes have been drilled. Broad geological details of the stretch are inferred from the

same and from the report “Design consultancy services of 4 laning Goa/Karnataka border-

Kundapur section of NH-17 from km 93.7 to km 283.300 in state of Karnataka” by

consultants M/s Aarvee associates Pvt. Ltd., Concessionaire M/s IRB West Coast Tollway

Pvt. Ltd., Independent Engineer M/s AECOM Rodic Consultants Pvt. Ltd. The design based

on above data is reviewed here.

SCOPE OF WORK:

To review tunnel design with special reference to following aspects:

Analysis and review of design of temporary liner components

Pros and cons of provisions

Construction methodology

Adequacy of Tunnel Support.

L-SECTION OF TUNNEL:

The L section depicting overburden is shown below for east and west tubes

.

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L-section THROUGH: EAST TUBE

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L-section THROUGH: WEST TUBE

GEOLOGY OF KARWAR:

The coastline of Karwar is arc shaped with intermittent rocky and sandy beaches (fig 1). The

main land has three major landforms namely, coastal, fluvial and denudation plains. The

coastal landforms are sandy and rocky beaches, tidal flats and estuaries. The fluvial

landforms are river Kali, flood plains of Kali River and channels. The denudation landforms

are mountains and pediplains.

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Fig. 1: Geomorphology of Karwar mainland

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Karwar islands are tropical with steep rock hills of about 20 – 60m height jutting out of the

sea. The coast of the islands is rocky and there are pockets of beaches in Kangigudda

slands due to accretion process (Fig 2). There are no sand-dunes. Migmatitic gneiss and

Granitoid with basaltic dykes are the rock types that constitute the hills of Karwar islands

with intermediate lateritic soils.

Fig 2: Gemorphology of Karwar islnads and their panoramic view

The littoral zone of the islands is dominated by silt followed by sand and clay; the carbon

content ranges from 0.033% to 3.7% and organic matter varies from 0.06% to 6.4%. The soil

types of the Karwar islands are alluvial and lateritic. The soil represent typical tropical

fericrete.

The shoreline of Karwar islands does not show any phenomenal change, but in the northern

portion of the mainland at the mouth of Kali river in the vicinity of Kurmagadagudda and

Shimisgudda islands and in southern coastline there are small changes in the coastline due

to erosion and accretion. Similarly Anjadeep and Shimisgudda islands having sandy

beaches show variation in the coastline. The rocky substratum of the islands and sandy

composite serve as ideal habitats for a variety of sessile and intertidal flora and fauna.

Geological InterpretationsThe area is predominantly occupied by rock types: granitic rocks, migmatites and granite

gneiss (PGC). These rocks are intruded by younger granites, dolerite and gabbro dykes.

Dykes of dolerite, gabbro are oriented N 55-800 W-S 550-800E.

Foliations’ are along N-S or N 200 W–S 200 E.

Three Lineament sets are along N 750–800W-S750-800 E, N 700E–S700W, N 300W–S 300E.

The geological map shows the rock type in Karwar to be granite.

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Geological InterpretationsThe area is predominantly occupied by rock types: granitic rocks, migmatites and granite

gneiss (PGC). These rocks are intruded by younger granites, dolerite and gabbro dykes.

Dykes of dolerite, gabbro are oriented N 55-800 W-S 550-800E

Foliations’ are along N-S or N 200 W–S 200 E.

Three Lineament sets are along N 750–800W-S750-800 E, N 700E–S700W, N 300W–S 300E.

The borelogs and corelogs are shown next.

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Based on geotechnical report the stratigraphy described below for Tunnel 1:

BH 1

DEPTH R.L

0

10 Soil and boulders.

12 Highly to moderately weathered granite gneiss of size medium to coarse grained and light in colour.

15.5 Moderately to slightly weathered granite gneiss with amphibolite enclave of size medium to coarse grained and light in colour

TUNNEL

32 Fresh granite gneiss of size medium to coarse grained and light in colour.

BH 2

DEPTH R.L

0

9 Soil and boulders.

10.5 Highly weathered granite gneiss of size fine grained and greyish in colour

14 Slightly weathered granite gneiss of size medium to coarse grained and light in colour

TUNNEL

15.5 Fresh granite gneiss of size medium to coarse grained and light in colour WITH AMPHIBOLITES

62 Granite gneiss of size medium to coarse grained and light in colour

BH 3

DEPTH R.L

0

2.7 Soil and boulders.

10


5 Weathered granite gneiss of size medium to coarse grained and

light in colour.

9.5 Fresh granite gneiss of size medium to coarse grained and light in colour

20 Fresh granite gneiss with vertical joints of size medium to coarse grained and light in colour also enclaves of amphibolites

TUNNEL

30 Fresh granite gneiss of size medium to coarse grained and light in colour.

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GEOTECHNICAL APPRAISAL:

Based on the 3 boreholes test data for the tunnel

The RMR values

BH No. 1 2 3

Above crown 51 77 71

Tunnel 29 77 65

Below invert 55 77 66

The Q values

BH No. 1 2 3

Above crown 3.5 5 4.9

Tunnel .33 5 5

Below invert 4.03 5 5

The RQD values

BH No. 1 2 3

Above crown - 100 98

Tunnel - 100 76


Joint sets seen in ‘Bore’ Photos

BH No. 1 2 3

Above crown 4 4 2

Tunnel 4 1 4

Below invert 4 4 2

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UCS Values (MPa)

BH No. 1 2 3

Above crown 49 203 85

Tunnel 56 60 133


K Values (Lugeons)

BH No. 1 2 3

Above crown 0.137 0 0.246

Tunnel 0.13 0.39 0

Below invert - 0

Table shows RMR values at Tunnel above crown and below invert. The Q values are given

in brackets.

Table RMR and Q Values

Location BH 1 BH 2 BH 3 BH 1 BH 2 BH 3

RMR Q

Above

crown

5177 71

(3) (5) (4.9)

Tunnel29 77 65

(0.33) (5) (5)

Below

invert

55 77 66(4) (5) (5)

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Joint Pattern:

Joints sets seen in core box are as follows:

BH 1 at levels 16.0m, 9.0m, 8.0m

BH 2 at levels 18.0m, 13.0m, 9.0m.

BH 3 at levels 19.0m, 23.0m, 28.0m

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COMMENTS ON THE QUALITY OF THE ROCK:

Comments quality of rock: The rock type is granite gneiss in all the boreholes. The

examination of RQD reveals that between RL 28 and 20 i.e. above crown the RQD values

are 70 to 100. The photos of the Borelogs confirm the above values. These values indicate

that fair to good quality as per IS code (11315 Part II).

UCS values between 28 and 20 RL are shown from BH1, BH2 and BH3 test results. These

values indicate the quality of rock as fair and good as IS code 13365 (Part I).

Permeability Values: The permeability values are less than 1 and joints are tight and gauge

filling is impervious at pressure 30m to 70m water head.

In the above crown portion the RQD varies from 70 to 100. This indicates the quality of rock

is fair and good as per IS code 11315 (Part II). The UCS values are in the range of 82 to 203

in the above crown portion. This shows the quality of rock as strong as per IS 13365 (Part I).

The RMR values shows in the above crown portion from 54 to 77. As per 13365 Part I

quality of rock as fair to good.

Q values are 5. This shows the rock is fair in nature.

RMR values: RMR values given are in the range of 54 to 77. The rock can be considered as

fair one, where as the description rock consider it as highly weathered in nature.

The design parameters selected based on statistical analysis for 90% and 50% occurrence

levels. The values selected are for these occurrence levels, is 36 MPa and 106 MPa.

The design is based on the geotechnical investigation report by Soil Tech Pvt. Ltd, Pune 6

bores in all are taken.

COMPARISION OF DESIGN PARAMETERS:

The deformation at crown is 0.06mm

The stresses observed at crown 0.261 kN/m2

Pillar shows stress level as 10.798 kN/m2

The depth of plastic zone is seen as 1.59m at crown.

Comparison of stresses observed in tunnel by PLAXIS 2D with Phase 2 software:

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So analysis stands vetted

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Tunnel 1

For design purpose, RMR value is considered as 60 for Tunnel, 50 for portals. GSI shall be

considered as 55 and 40 respectively for Tunnel and Portal.

The Q values are 8 – 10 tunnel portion and (1 – 3) in Portal portion, being the weakest

values. For design purpose, however, for North portal, Tunnel and South portal, Q values

shall be considered as 2, 6 and 3 respectively.

Based on the core box photos given in the geotechnical report the joints sets are

tabulated below along with graphs for BH 1, BH2 and BH3 of Tunnel 1:

17


Based on the Lugeon Value given in the geotechnical reports are tabulated below

along with graphs for BH 1, BH2 and BH3 of Tunnel 1:

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FINITE ELEMENT ANALYSIS:

The FEA is carried out for 2 failures criteria using Phase2 software. Mohr-Coulomb and

Hoek-Brown. The k value -1 is selected for design. The method proposed is elastic analysis,

plastic analysis. Twin tunnels at a distance of 20m from each other were taken for review.

Following tables produced from “Design consultancy services of 4 laning Goa/Karnataka

border-Kundapur section of NH-17 from km 93.7 to km 283.300 in state of Karnataka”,

Tunnel 1 Design Report by consultants M/s Aarvee associates Pvt. Ltd., Concessionaire

M/s IRB West Coast Tollway Pvt. Ltd., Independent Engineer M/s AECOM Rodic

Consultants Pvt. Ltd are compared with the results obtained from PLAXIS 2D with given

material data.

PLAXIS ANALYSIS:

TUNNEL 1

Identification   Granite 1 Granite 2 Granite 3

Identification number   1 2 3

Drainage type   Non-porous Non-porous Non-porous

Colour  

γunsat kN/m³ 28.20 28.50 28.10

γsat kN/m³ 28.20 28.50 28.10

E kN/m² 17.63E6 17.63E6 12.90E6

ν (nu)   0.2900 0.2800 0.3000

σci kN/m² 82.00E3 82.00E3 60.00E3

mi   29.00 29.00 29.00

GSI   45.00 72.00 40.00

D   0.000 0.000 0.000

ψmax ° 11.00 11.00 11.00

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σψ kN/m² 0.000 0.000 0.000

Strength   Rigid Rigid Rigid

Rinter   1.000 1.000 1.000

K0,x = K0,z   Yes Yes Yes

K0,x   1.000 1.000 1.000

K0,z   1.000 1.000 1.000

Identification   Lining

Identification number   1

Colour  

Material type   Elastic

Isotropic   Yes

End bearing   No

EA1 kN/m 5.700E6

EA2 kN/m 5.700E6

EI kN m²/m 19.00E3

d m 0.2000

w kN/m/m 4.800

ν (nu)   0.1700

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Geometry of tunnel Principal effective stresses

Deformation Plasitc point

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ANALYSIS AND REVIEW OF DESIGN OF TEMPORARY LINER COMPONENTS:

Sr. No.

Design Basis Impact

1 UCS values from geotechnical data are

subjected to statistical analysis. Values

that exceed 50% and 90% values are

picked up as 96 MPa and 35 MPa

respectively.

Such an approach leads to conservative

design. Incidences of such low values is a

‘localised’ event. Moreover, depth wise

UCS pattern is ignored

R eply: UCS values mentioned above are not related to BH 1.

2 UCS vs E Graph shows a negative

slope.

Such a trend is not common in rock

mechanics

Reply: The actual trend is modified by neglecting values which lead to a positive

slope. Since different models with mean and minimum values are considered for

assessing the rock mass behavior, it does not change the predicted rock mass

behavior in Phase 2 and Plaxis.

3RMR vs Q basis is not linear but ‘log’.

The axes are mismatch with realistic

values

Reply: The typographical mistake in figure 53 can be read with "Linear" as

"Logerthemic" and interchanging Q on X-axis and RMR on Y-axis.

4 Hoek and Brown and Mohr- Coulomb

failure models are selected.

Sensitively analysis shows different

response from both the methods

5 Check for variations of σ1 is affected

Hoek and Brown

Mohr-Coulomb

HB 90 is not appropriate

6Check for variations of σ3 is affected

Hoek and Brown, Mohr- CoulombHB 90 is not appropriate

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Sr. No.

Design Basis Impact

Reply: Please elaborate how HB 90 is not applicable.

7 Check for variation of shear strain is

done

RMR, Q values tabulated show strange

pattern. RMR – 70, Q = 4, 14,ok

8 Maximum support pressure k = 1

Reply: Not applicable.

9 Approach used is

Reply: Approach used in Rocscience Phase 2 is already discussed in the report.

10 Grade of concrete M 25 is considered It’s ok

11 Grade of steel Fe 500 is considered It’s ok

12 Shotcrete M25 is considered It’s ok

13 F.R.C.S. M25 is considered It’s ok

14 Plastic analysis shows It’s ok

15 Hand calculation shows It’s ok

16 Earthquake calculation for Zone III. Adequate

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SUPPORT SYSTEM ANALYSIS:

1This is required if rock is considered as

highly weathered

But the rock is not highly weathered as

indicted in design but it is of RMR 60.

2This is a provision for making the rock

mass homogeneous

This provision may be required in 20%

length of the tunnel not for the entire length

3Provision is indicated throughout length

of the tunnel.

The stress level indicates that only rock

bolts are adequate.

4 This enhances strength factor

Strength factor calculation show

contribution of rock bolt to be additional

provision

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PROS AND CONS OF PROVISION:

Spilling:

In poor quality rock as seen in the BH-

1 spilling will assist in excavation

If the portal is shifted by 30m rock shall be fair

type and this provision is not necessary

Reply: If we shift the portal location,buildings above the tunnel will be affected and also

keeping in view of safety of D.C bungalow and highly jointed nature of rock mass and nil Q

values obtained above crown portion in the B.H 2, spiling has been provided in this stretch/

reach.

Shotcreting:

The Sealing and SFRS are provided.

In NATM method the rock strength

mobilized as well as shotcrete strength

are basis of liner design hence

required

This is bare minimum and if not provided leads

to rock falls in rock mass. However, thickness of

shotcrete has to be adequate enough to arrest

the, induced stresses.

Reply: The thickness of shotcrete is worked out as per design analysis keeping in view rock

mass nature and it is to state that the thickness provided is sufficient to take care any

induced stresses.

Steel Ribs:

Steel ribs are provided in the portal in

30m length

Considering rock quality provision for 5m length

shall be sufficient.

Reply: We have provided steel ribs for 25m length and not for 30m. Please refer tender

document Cl.4.19, which specifies 25m length at entry and exit of each tunnel will be

strengthened with RCC Portals. Accordingly it is proposed at all portal locations. Further it is

also suggested that tunnels were strengthened up to twice the tunnel diameter. Keeping in

view of the presence of DC Bungalow and mixed geology, steel ribs with pipe roofing have

been provided in between BH No's 1 & 2.

Rock Bolts:

Rock bolts are provided in the portal in

30m length, 4m long

Considering rock quality provision for 5m long

rock bolts shall be sufficient.

Reply: Rock bolts were provided in between steel ribs, to take care off any unstable wedge

failures.

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Grouting:

It is considered as dry tunnel grouting

is not provided

Whereas seepage is to be arrested in rainy

season this provision in essential.

Reply: Normally on the round shaped granite hillocks, run off will be more than infiltration.

However, depending on seepage conditions through any adverse geological features

grouting needs to be done as per geologist/ designer's advice, during excavation.

Bottom strut:

For poor quality rock this is providedRMR and Q values below invert, however,

indicate not required

Reply: Rock quality below invert is very poor with Q values varying from 0.00- 0.33 as per

borehole data of BH 1 and 2. Numerical modelling has also indicated Invert heaving. As

such bottom strut is provided.

The provision of 200mm (SFRS): thick permanent lining is indicated

Liner is indicated to be provided even when in the 2nd tube excavation is in progress

This shall be required

Blasting induced cracks in SFRS are possible. Hence the permanent lining shall be deferred until all the excavation is complete, well over 70m in advancement.

Reply: Normally lining shall be taken up as per construction schedule. Safe distance

between blasting face and lined section shall be maintained as per established data for such

rock and specific blasting pattern.

SUGGESTIONS:

The rock bolts are required only in shattered zone by intersecting joints or vertical joints.

The rock mass requires reassessment of RMR during excavation and adequate support shall be provided.

Rework out the lining system as joints lineaments are entry points for rainwater which is considerably high in Karwar.

Provision of drainage system is essential.

26


CONSTRUCTION METHODOLOGY:

Portal:

NATM method is suggested for controlling deformation at ground. Active support system is

in the form of rock bolts, shotcrete and steel ribs. Single or double layer of spile umbrella is

suggested. Multiple heading method is suggested. For design, however top heading is

considered.

Tunnel

Chainage 106.99 km to 107.223 and chainage 106.980 to 107.209 Left tube sequence of

excavation is top heading excavation support system consisting of rock bolts and shotcrete,

followed by excavation of benching and installation of support viz rock bolts, shotcrete. This

is followed by final tunnel lining. After this same steps for right tube from chainage 106.99

km to 107.223 and chainage 106.980 to 107.209.

The above steps but with shotcrete and rock bolt thickness altered.

Seepage provision not there.

Comments:

The steel ribs in 30m length are not required and provision for 5m shall suffice.

Bolt length shall be 5m.

Full face excavation is possible with provision of temporary (initial) lining.

For collectors bungalow with the vibration control measures suggested additional measures

are not necessary.

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ADEQUACY OF TUNNEL SUPPORT:

Adequacy of tunnel support is checked with respect to

Elastic Analysis

Plastic Analysis

Earthquake Analysis

And empirical relations.

The adequate modifications are suggested for taking care of the induced stress levels after the excavation in.

Precautions for collector’s Bungalow:

The cover over crown is more than 14m. As such, the effect vibrations has to be viewed in

the perspective of delay in blast energy during travel from R.L. 20 to G.L. following

precautions shall be useful.

Restricting charge per delay to not more than 4kg.

Presplitting the rock before blasting

Controlled full face blasting.

Measuring the vibration level (PPV) at collectors Bungalow and monitoring the charge levels suitably.

The rock quality is “FAIR” and appropriate initial lining is indicated

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29


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EXECUTIVE SUMMARY:

SUPPORTS SYSTEM FOR KARWAR ROAD TUNNEL1

Introduction:

Two parallel Tunnels – Tunnel No. 1 East Tube and Tunnel No. 1 West Tube are being

constructed on the Goa/Karnataka Border to Kundapur Section of NH 17. This report is for

re-assessment of the Tunnel Supporting System.

Location of Tunnels:

The Tunnels are 20 m apart and are staggered in plan as follows:

East Tube West Tube

North Portal Chainage, m 107,000 106,990

South Portal Chainage, m 107,223 107,209

Tunnel Length, m 223 219

Since the tubes are located only 20 m. and staggering is only to the extent of about 10 m.

the data revealed by exploratory boring along Common Centerline has been considered and

is alright.

Exploratory Bore Hole Data:

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For design of Roof supporting system, least of the RMR Value i.e. least of RMR at tunnel

level and in zone 14 m. above crown is being considered as follows:

North Portal RMR 50 for 40 m. zone

South Portal RMR 60 for 40 m. zone

Tunnel RMR 60 for entire length

Existence of Collectors Bungalow above West Tube should not be a matter of concern.

Elevation of the bungalow is about 65 m. At that location, tunnel crown will be at an elevation

of about 19 m. Leaving a vertical gap of about 46 m. out of which hard rock will be 31 m.,

soft rock about 5 m. and top soil about 10 m. Rock has a very high RMR of 77 i.e. Good

Class. If controlled blasting is undertaken, the bungalow will not be damaged.

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Report for Karwar Tunnel 1Noble Geo-Structs Project No. S 16029August 31, 2015

APPENDIX I CORE LOGS

Borelogs and Corelogs for Tunnel 1

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APPENDIX II

FINITE ELEMENT ANALYSIS DATA USED FOR PHASE 2

Table 1: Selected Rock Mass Parameters for Numerical Analysis

Table 2: Properties of Rock Joints used for Numerical Analysis

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Table 3: Computation of the ratio of Maximum principal stress to uniaxial compressive strength of intact rock

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Table 4: Tensile strength as per Mohr-Coulomb failure criteria

Table 5: Support pressure requirements using bolts and steel ribs to resist the rock load for jointed model

Table 6: Support pressure requirements using bolts and shotcrete to resist the rock load for general model.

Shotcrete

47


Table 7: Rock mass properties for this analysis based on Hoek and Brown

Table 8: Rock mass Strength computations

Table 9: Equivalent rock mass properties

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Table 10: Test results on intact rock samples of BH3 at km: 107.210

Table 11: Test results of cohesion and friction of rock mass

Table 12: Selected Rock Mass Properties for Numerical Analysis

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.

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TUN 1

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