MAZAGONMAZAGONDOCK SHIPBUILDERS LIMITED DOCK … · 2019-09-20 · Logging visually identifiable...

MAZAGONMAZAGON DOCK SHIPBUILDERS LIMITEDDOCK SHIPBUILDERS LIMITED

MARINEMARINE GEOTECHNICAL INVESTIGATION FORGEOTECHNICAL INVESTIGATION FOR THETHE

PROPOSEDPROPOSED EXTENSION OF NAVIGATIONAL CHANNELEXTENSION OF NAVIGATIONAL CHANNEL

CONTAINER TERMINALCONTAINER TERMINAL

WAPCOS Limited(A GOVERNMENT OF INDIA UNDERTAKING)

Swastik, Gulmohar Path, Near SNDT

College, Erandawane, Pune-411004: 020 - 25444796

Fax : 020 – 25444600

Email : [email protected]

June - 2017

GEOTECHNICAL REPORT

100405

Typewritten Text

Enclosure - 29

100405

Typewritten Text

CONSULTANCY SERVICES FOR GEO TECHNICAL SURVEY (GTS)

FOR NAVIGATIONAL CHANNEL IN MDL

GeotechnicalReport Page1

MARINE GEOTECHNICAL INVESTIGATION FOR THEPROPOSED EXTENSION OF NAVIGATIONAL CHANNEL FROM MDL’S WATERFRONT TO THE

OFFSHORE CONTAINER TERMINAL BYDREDGING AT MAZAGON DOCK LIMITED (MDL), MUMBAI

1.0 INTRODUCTION

1.1 Description of proposed Project Characteristics

Mazagon Dock Shipbuilders Limited is India’s prime Warship building yard under the Ministry of

Defense, Government of India. MDL intends to create a navigational channel of depth 6.0 m CD

for movement of vessels from MDL’s waterfront to the Offshore Container Terminal (OCT) of

Mumbai Port Trust (MbPT). In addition, MDL has intend to deepen the remaining area of

waterfront i.e the area between the North wall of new wet basin and the Northern boundary of

the Alcock yard, so as to provide easy movement of vessels throughout their waterfront.

In this regard, MDL have approached and entrusted WAPCOS Ltd. to undertake Marine

Geotechnical Investigations, based on the Geo Physical Survey undertaken by CWPRS, to find

out the sea bed strata and to ultimately estimate the quantity of soil and rock dredging

separately for the project area.

1.2 Purpose

The purpose of this study is to determine the general seabed stratigraphy by drilling ten (10)

exploratory boreholes of maximum 7m to 10m deep. The boreholes are drilled to collect

information on soil and rock bed level to draw their profile with respect to CD. This is done to

ultimately quantify soil and rock dredging material separately.

1.3 Scope of investigation

The work entails carrying out a campaign of geotechnical site investigation including the following:

� Mobilization of machinery and manpower along with the Spud Barge mounted with

hydraulic drill rig, water pump, testing tools, accessories, power pack, store house etc. to

carry out marine boreholes and insitu tests.

� Survey and precise positioning of the borehole locations using DGPS.

� Floating out and shifting of the barge using tug boat.

� Sinking of 10 nos. boreholes from existing sea bed level in the proposed area.

� Carrying out Standard Penetration Tests (SPT) in the boreholes at regular interval.

� Sampling (Disturbed) of soil in the boreholes.

� Logging visually identifiable lithological and engineering characteristics of soil samples and

rock core samples.

� Packing, labeling and dispatching the soil samples and rock cores to laboratory.

� Laboratory testing and analysis.

� Preparation and submission of geotechnical investigation report.




2.0 SITE CONDITION

2.1 Site General Description and Local Geology

MDL is located in the Mumbai Harbour (Latitude 18� 58’ N, Longitude 72� 50’ E) on the west

coast of India. The harbor is protected by the mainland of Konkan to its east and north and by

the island of Salsette to its west. The harbor opens to the south to the Arabian Sea.

The principal rocks in Mumbai are volcanic and a variety of trap rocks are found here. The traps

are interstratified with Sedimentary rocks of fresh water origin. The entire Mumbai area is

occupied by Deccan basalt flows and their acid and basic variants, poured out between the late

Cretaceous and early Eocene times. The basaltic flows are horizontally bedded and are more or

less uniform in character over wide areas. Certain extrusive and intrusive mafic types are

associated with basalt’s and are found in the Mumbai Islands and its vicinity.

In general the geology of the proposed site is described as being comprised of granular soil of

sedimentary deposits with silty clay at the surface and completely weathered to highly

weathered Basalt rock up to the drilled depth.

2.2 Site surface description

The drilling of boreholes was carried out with the help of spud barge and the levels were taken

with respected to CD. It was found that the soil bed level varies from +0.56 m CD to 1.5 m CD

and the rock bed level vary from 3.5 m CD to 10.5 m CD.

2.3 Description of underground obstruction

Underground obstruction during drilling may encounter in different forms like presence of

boulders or cavities or highly fractured zone where no water circulation occurs. In this

investigation no underground obstructions were encountered.

3.0 FIELD INVESTIGATION

The equipment and manpower required to undertake work were mobilized to site on 2nd May

2017. The field investigation was carried out to determine the engineering characteristics of the

subsoil strata including a reconnaissance of the project site, drilling of exploratory borings, and

recovering representative soil samples.

3.1 Summary of operations

The general subsurface conditions were investigated by drilling ten (10) exploratory borings. The

boreholes were drilled to a depth of 7m to 10m. The borehole locations were determined and

established in the field by WAPCOS.

The drilling work was conducted by means of rotary drilling techniques with water flush using

mechanical rotary drilling rig with the help of pontoon.




The depths of boreholes together with the descriptions, depths of strata encountered and

levels at which samples were recovered are indicated in the accompanying boring log sheets in

AppendixA.

3.2 Description of sampling procedures

3.2.1 Disturbed soil Samples:

These are the samples in which the natural structure of the soil gets disturbed during sampling.

However, these samples truly represent the composition and the mineral content of soil. The

disturbed soil can be used to determine the index properties of soil, such as grain size, plasticity

characteristics and specific gravity. Split spoon sampler was used to collect these samples. In

this investigation the disturbed samples were collected during Standard Penetration Test for soil

classification and identification.

3.2.2 Undisturbed soil Samples:

These are the samples in which the natural structure of the soil and the water content are

retained. Undisturbed samples are used for determining the engineering properties of soil,

such as compressibility and shear strength. In this investigation undisturbed samples of

cohesive soils were collected by using Shelby tube for Laboratory analysis.

3.2.3 Rock Samples:

Rock samples were collected by core drilling to obtain rock cores. These rock core samples

were further used to defined the quality and strength of rock. In this investigation, locations

where rock was encountered, single tube core barrel with core bit was used to collect the rock

sample.

3.3 Description of field test

3.3.1 Standard Penetration Test

In the proposed work Standard Penetration Test (STP) was conducted as field test. During drilling,

SPT was carried out at regular depth intervals in order to assess the N value and relative densities

of the existing soils.

In this test, the number of blows required to drive a split spoon sampler with a 63.5 kg free falling

weight for a total penetration distance of 450 mm in increments of 150 mm is recorded. The

number of blows required to drive the split spoon sampler for the first 150mm is referred to as

seating blow count and does not enter into the calculation of 'N' value. The 'N' value is the

number of blows required to drive the split spoon sampler for the next 300mm (i.e., from 150 mm

to 450 mm).

The depths at which the SPTs were carried out and resulting 'N' values are given on the

accompanying boring log sheets in AppendixA.




3.4 Logs of Borings

A total of ten (10) boreholes were drilled at the proposed locations. The details of complete

description, thickness of all strata, locations referenced to coordinates, ground water elevation

and standard penetration test values (SPT), total core recovery value (TCR) and Rock quality

designation value (RQD) are all mentioned in the prepared bore logs, which are presented in

Appendix A.

3.5 Location Plan

The details of borehole location, test locations with their coordinates are represented in

the following table and in Fig.1.

COORDINATES OF BORE HOLE LOCATION

SR NO.

LATITUDE LONGITUDE WGS

84

UTM

43

UTM CO ORDINATES

DEG. MIN SEC DEG. MIN SEC EASTING NORTHING

1 18 57 59.60 72 51 26.47 43 274400 2098500

2 18 58 6.03 72 51 19.56 43 274200 2098700

3 18 58 12.45 72 51 12.64 43 274000 2098900

4 18 58 5.93 72 51 11.01 43 273950 2098700

5 18 58 10.72 72 51 4.12 43 273750 2098850

6 18 58 10.56 72 51 9.25 43 273900 2098843

7 18 58 2.64 72 51 16.18 43 274100 2098597

8 18 58 11.22 72 51 16.07 43 274100 2098861

9 18 58 5.99 72 51 16.14 43 274100 2098700

10 18 58 2.66 72 51 9.35 43 273900 2098600




Fig 1: Locations of Boreholes




4.0 SUBSURFACE CONDITIONS

4.1 Subsurface Stratigraphy

The stratigraphy observed from the proposed investigation site indicates the top deposit is of

natural soil, it contains coarse to fine grained soil at varying depths in all the boreholes. After

this depth a rock layer of completely weathered to highly weathered Basalt rock is encountered

in the borehole up to the terminated depth of borings.

4.2 Subsurface material properties

The soil conditions encountered in the test borings are described briefly in the following

paragraphs. The soil boring logs should be referred for more detailed description of soil

condition in the test borings. The letters in parenthesis after the soil description on the boring

logs in the Appendix are the soil classification in accordance with the Indian Standard

Classification System (IS 1498: 1970).

The boreholes drilled at the site disclosed granular material and rock; these are categorized in

different layers as follows:

Stratum One: Granular Materials

First stratum of subsoil profile is Sedimentary soil deposits of granular material or residual soil.

The stratum has Silty Clay, Silty Sand, gravel with sand, Silty gravel with Sand soil. This stratum

has variation in depth in each borehole.

Based on SPT N values these soil deposits have been classified as very loose to very dense in

condition.

Stratum Two: Completely weathered to highly weathered Basalt Rock:

Second stratum of subsoil profile is completely weathered to highly weathered Basalt rock. This

stratum starts from varying depth in this vicinity of this area. The boreholes were terminated in

maximum 2 m depth in this rocky stratum.

Based on the Rock quality designation value (RQD) the rock obtained is classified as very poor.

Based on the unconfined compressive strength, these rocks have been classified as very

weak to strong rock in strength.

5.0 LABORATORY TESTING PROGRAM

In addition to the field investigation, a supplemental laboratorytesting program was

conducted to determine additional pertinent engineering characteristics of the foundation

materials necessary for analyzing the behavior of the proposed structure.

The laboratory testing program included:

a) Grain size distribution




b) Atterberg limits

c) Swell tests

d) Direct shear test

e) Chemical tests.

The results on selected samples obtained from all the test borings from ground level to terminal

depths were analyzed and included as appendices to this report.

The grain size distribution of representative soil samples to determine by sieve analysis in

accordance with IS 27201985 are included in Appendix B.

The Atterberg limits of representative soil samples to determine the liquid limit, plastic limit and

plasticity index in accordance with IS 27201985 are included in Appendix B.

The Unconfined compressive tests of representative soil samples to determine the shear

strength parameter in accordance with IS 27201985 are included in Appendix B.

The Triaxial shear tests of representative soil samples to determine the shear strength

parameter in accordance with IS 27201985 are included in Appendix B.

Unconfined compressive strength of representative rock samples were carried out along with

the physical analysis such as specific gravity, water absorption and porosity as per IS 9143 –

1979, the results of such tests are included in Appendix B.

6.0 DETAIL OF SUBSOIL DREGING REQUIREMENT:

6.1 General:

This Marine investigation was carried out to check the extent of Soil and rock strata exist in the

vicinity. CD level is taken as bench mark for the depth of soil bed level and rock level during this

investigation. The profile of soil/ rock strata shows that maximum dredging required is in soil

strata only however in area of BH5, 6, 9 & 10 required dredging in Rocky strata to obtain a

dredge level of 6.0m from CD level.

6.2 Detail profile subsoil strata:

Chart below shows the details of subsoil stratum condition below the CD level.




6.3 Details of subsurface soil/rock depth.

Borehole

Nos.

CD

Level

Soil

Bed

Level

Rock

Bed

Level

Thickness of

dredging

required in

soil (m)

Thickness of

dredging

required in

Rock (m)

Remarks

1 0 0.99 10.5 5.01 0 very loose soil

2 0 1.5 7.5 4.5 0 very loose soil

3 0 0.26 6.36 5.74 0 very loose soil

4 0 0.74 6.74 5.26 0very loose to very

dense soil

5 0 0.56 4.34 4.91 1.65

very loose to medium

dense soil and Rock

very weak to

moderately weak in

strength

6 0 0.54 4.46 5 1.54

very loose to medium

dense soil and Rock

moderately strong in

strength

7 0 1.16 6.16 4.84 0 very loose soil

8 0 0.22 7.08 6.22 0 very loose soil




9 0 1.1 4.9 3.9 1

very loose soil and

Rock very weak in

strength

10 0 1.5 3.25 1.75 2.75

very loose to dense soil

and Rock very weak to

Strong in strength

7.0 CONCLUSION AND RECOMMENDATIONS

From the above investigation it is seen that for construction of navigational channel client to

assign a dredging company by considering the following condition of subsoil.

a) It is seen that approximately 85% dredging work is in soil where the soil condition is very loose

to dense in condition.

b) And approximately 15% of the dredging work is in Rock, where the rock condition is very weak

to strong in strength.

Clause 6.3 provides the details of depth/ thickness of dredging required in both soil/rock to

obtain the required level.































































































































BOREHOLE NO.: MBH – 1





BOREHOLE NO.: MBH 3




















SAMPLES COLLECTED FROM BOREHOLE NO.: MBH – 1






















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