*A National Highways Authority of India f l

b

7. Zonsultancy Services for Feasibility study and Detailed Project Report

P or 416 Laning of Karur= Madurai section of NH.7 from Km 30518 to 42616

- in the State of Tamil Nadu (Consultancy Package C-ll 111)

r- CQMT?hCs PACYACE PIS R2 (TM)

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* VOLUME I11 : MATERIAL REPORT

January 2005

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Table of Contents

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1

TABLE OF CONTENTS

CHAPTER - I S. No Description

1.0 MATERIAL INVESTIGATION

1 .I Introduction

1.2 Project Description

1.3 Objective Of Material Investigation

1.3.1 investigation for Embankment and Sub grade

1.3.2 Pavement Materials

1.3.3 Stone Aggregate

1.3.4 Sand

1.3.5 Cement, Steel and B i m e n

CHAPTER - II 2.0 SUBGRADE INVESTIGATION

2.1 Introduction

2.2 Project Description

2.3 Sub grade Soil Investigations

2.3.1 Methodology

2.3.2 Results of Investigations

2.3.3 Field Tests on Existing Alignment

2.4 Recommendations

Page No.

I

<'-.

Final Detailed Project Report Table of Contents i Contract Package: - NS 82 (TN) Volume Ill: Material Report

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-k

Fig. No

Table No

LlST OF FIGURES

Description Page No.

Project road and & location of various quarries and borrow areas

Soil Classification

Plasticity lndex

MDD of Borrow Area Samples

CBR of Borrow Area Samples

Soil Classification

Plasticity lndex

FDD & MDD

FMC & OMC

Soaked CBR at 97% MDD

LlST OF TABLES

Description

Test Results of Borrow Area Samples

Test Results of Gravel Samples

Test Results of Aggregates Samples

Test Results of Sand Quarry Samples'

Borrow Areas for Embankment I Sub grade

Summary of Test Results

Results of CBR & SNSG from DCP Tests

Summary of Test Results

Summary of Test Results

Page No.

h

Final Detailed Project Report Table of Contents A

ii Contract Package: - NS 82 (TN) Volume Ill: Material Report

A

Chapter 1 : Material Investigations

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e k ~ l P l Consultancy Services for Feasibility study and Prepamtion of DPR --Bag Y

1.0 REPORT ON MATERIAL INVESTIGATIONS

I I INTRODUCTION

The Ministry of Road Transport and Highways (MoRT&H), Govt. of lndia has taken up the development of various National Highway Corridors where the traffic intensity has increased significantly thereby necessitating capacity augmentation for safe and efficient movement of traffic. This Project is a part of North - South corridor connecting Srinagar in J&K State to Kanyakumari in Tamil Nadu. National Highways Authority of lndia (NHAI) has been entrusted to implement the development projects for these corridors. The work of conducting Feasibility Studies and Preparation of Detailed Project Report for Four I Six laning from Karur (Km 305.800) to Madurai (Km. 426.660), a section of NH 7 has been entrusted to the Joint Venture of BCEOM - Aarvee Associates.

For the convenience in construction, the present project corridor has been divided into three packages. They are:

Package NS-80 (TN): Km 305.800 to Km 345.000 Package NS-81 (TN): Km 345.000 to Km 381 .ZOO Package NS-82 (TN): Km 381 .ZOO to Km 426.660

In this chapter, the data pertaining to the Construction package: NS-82 (TN) is presented.

1.2 PROJECT DESCRIPTION

The road section from Km 381.200 to Km 426.660 of NH-7 (Package NS82 (TN)) is taken up for conducting detailed engineering studies for rehabilitation and up-gradation of existing 2 lane to 4 lane divided carriage way highway with improved traffic capacity. Suitable construction materials (such as embankment material, sub-grade material, Granular sub base material, metal quarries and Aggregate crushers) investigations form an essential part of studies conducted for identification of potential sources with minimum lead and easy approach to the construction site. The study involves assessing the requisite quantity available in respect of estimated quantity.

The investigation entails carrying out the visual locations of Borrow areas, locations of quarries etc. with approachable minimum lead, collection of samples, laboratory testing for assessing their quality, and suitability, and assessment of their quantity available for construction purposes.

The investigation and testing of materials is carried out in accordance with the provisions of TOR clause 4.1 1.5. A mass haul diagram is also prepared and enclosed indicating locations of selected Borrow areas, quarries etc. haulage routs with minimum lead approximate quantity available against the requirement and the ownership of the Borrow areaslquarries etc. The following sections discuss about the details of samples collection, laboratory tests carried out and their results and suitability of materials.

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1.3 OBJECTIVE OF MATERIAL INVESTIGATIONS

Basic objective of material investigations is to identify the potential sources of construction materials along the project stretch, to yield adequate quantity of materials which are suitable for various pavement layers viz. embankment, sub grade, sub base, base, etc.

Suitable sources have been identified along the project stretch by local enquiry. However, consultants have carried out tests on selected sources to find their suitability for use. Sufficient number of quarries has been identified to verify availability of materials within economical leads.

The information on the materials sources was summarized with the following objectives:

ldentification of source locations indicating places and the status of quarries whether in operation or new sources. Identification of requirements for road pavements, shoulder works, cross drainage and other works. Material specification and characteristics. Testing and evaluation of materials for use in works.

Consultants have identified a number of quarries for stone, sand, gravel and borrow areas for earth. More borrow areas are available along the roadside. The samples were tested in the laboratory to evaluate their suitability for road construction. A sketch showing the project road and location of various quarries and borrow areas along with the leads is given in Figure 1 .I.

1.3.1 Investigation for Embankment and Subgrade

Material was collected from the borrow areas and tests were conducted to determine the following parameters:

Grain size analysis Atterberg's limits Compaction characteristics Strength characteristics

Table 1.1 presents details of location of borrow areas for embankment and subgrade. The analysis brings out the following

Soils are predominantly GC (29%) and SC(71%) Plasticity index ranges from 15% to 18% Maximum dry density is ranges from 1.98 gmlcc to 2.17 gmlcc CBR was found to be ranging between 15% to 35%

Figure 1.2 to Figure 1.5 shows the location wise variation of Plasticity Index, Maximum dry density and CBR respectively. The summary of test results of borrow area samples furnished in Table 1.1 and Gravel samples in Table 1.2. The details of quarry and borrow locations are given in Table 1.5.

It can be inferred from above that all borrow soils are suitable for Embankment an

pter - 1 : Material Investigations

Volume Ill: Material Report

. . . . . .,.. ,-, , . . I

h me=- 4 /6 Laning of Karur - Madurai Section of NH-7 , m-- Consultancy Services for Feasibility study and Preparation of DPR

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PROJECT ROAD - MAJOR ROADS ~~ ~ RIVER/STREAM -- NH/SH HIGHWAYS- OTHER ROADS - - RAILWAY LINE - AGGREGATE QUARRY SAND QUARRY

GRAVEL QUARRY A BORROW QUARRY@

rr

Figure 1 .I. The project road and location of various quarries and borrow areas - - . c= :. . * : ., . '\., , 1, i ,, ' 3

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Final Project Report Chapter - I : Material lnve~~&s. : :' ' .- "\jL5z~~&l I

h Contract Package - NS82 iTN) Volume Ill: ater rial ~ e p o i '

4 /6 Laning of Karur - Madumi Section of NH-7 Consultancy Services for Feasibility study and Prepamtion of DPR 3

Figl.2 Soil Classlflcatlon

Fig 1.3 Plasticity Index

Plasticity index

18.5 -

M a x i ~ m Dry Density

18 - 17.5 -

17 - 16.5 -

b 16 - 15.5

15 14.5 -

14 13.5 7

\

\

-. -.

-.

..-- Final Project Report Chapter - I: Material Investigations , .> y . . t 0 f 1 1 Contract Package - NS82 (TN) .

. , Volume Ill: Material Report !

4WlO 42114 39312 39712 40510 412/900 4234

Chainage

2 2

2.15 - 2.1 -

- *. A

0 2 0 5 - \

2 -

1.95 -

1.9 -

\

I

I 1.85 7 1

400/0 42114 39312 39712 40510 412/900 4234

Location of B o r n h a

Fig 1.4 MDD of Borrow Area Samples

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Fig 1.5 CBR of Borrow Area Samples

Soaked CBR (%)

1.3.2 Pavement materials

40 ~

35 - 30-

iz 25 - L 0 15 -.

10 - 5 - 0 1

The pavement has been designed to comprise the following materials:

h / \ / -1 -

SurfaceMlearing course - Bituminous Concrete Base Course - Dense Bituminous macadam I Wet Mix Macadam Sub-base Course - Granular sub-base

For the above components, the basic materials available from natural I quarry sources are shown in Table 1.3 and analysis brings out the following.

W O 42114 39312 30712 4030 412/900 4 W 4

LocatJon of Bomm Area

1.3.3 Stone Aggregate

Samples have been collected from the existing quarries and crushers to find their suitability for use in the cement concrete, sub base, base and wearing courses.

The aggregates have been subjected to the following tests:

Impact value Specific gravity and water absorption Stripping value Soundness

In the primary investigations, the aggregates seem to be having a stripping value of more than 5%. It may be required to add anti stripping agents to bitumen during construction of asphalt courses. The test results are furnished in Table 1.3.

1.3.4 Sand

Sand has been collected from three quarries and all the quarries satisfy requiremen II sand, which is ideal for reinforced concrete. But, there is a recent order that san only through PWD

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to manufacture "crusher sand " by installing additional machinery along with stone crusher. The test results are furnished in Table 1.4.

1.3.5 Cement, Steel and Bitumen *.

Cement, bitumen, steel etc are the manufactured materials. Bitumen is produced indigenously in lndia and is generally supplied from the nearest oil refinery. Regular supply of bitumen can be satisfactorily met by advance agreements.

Cement conforming to BIS specifications can be procured directly form factories or can be purchased from dealers of the factories in all the major towns along the project road. The reinforcement steel both CRS and ordinary Tor steel of different grades conforming to BIS specifications is available. Hence there is no difficulty in respect of its availability in this project.

The nearest sources are:

Bitumen Madras Refinery 1 Cochin refinery Cement India Cements, Chennai. Steel Rashtriya lspat Nigam Limited (Visakhapatnam Steel Plant)

- d

Final Project Report Chapter - I: Material lnve 6of 11 Contract Package - NS82 (TN) Volume Ill: Material Report

Table 1.2 Test Results of Gravel Samples

WI TYp.

GC

GC

A(tnbwp's U m b N.prw

'mi.a- RbM

Slaw Analysis (Cum X P.ulw)

G4

Roctor Test lm

PI(%)

20

19

)

35

37

CBR T n l

YDD onJ=

2.10

2.092

PL (K)

15

18

Somkkapatti

In Behneen to Kmngothopu - Andipatly village MI NH-7

CBR VALUE

(X)

30

29

10.3

8

2 0 mm

34

37

75.0 mm

100

100

Wsturm -4- .oc*lw(%l

12.6

10.5

Palanl - SebampaW roadofy0-810km

Along mad side ( NH-7) of Kodal mad

0.425 mm

29

25

53.0 mm

100

BB

19.0 mm

89

90

0.075 mm

25

27

4.75 mm

48

46

26.5 mm

96

94

0.5 nun

73

76

( h . 1

39412

41012

2.36 mm

40

40

R

L

(Km.)

8.5

0.2

Table 1.3 Test Results of *qgmgah Samples

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Sorakkapattl

ParsyaMIplpl .

~ u u y ~ o u t i o n

P a w - Sebsmpatly road of 14n kn

Avanaipuram- Twukwhrn Road

DESCRIPTIONOF SAMPLE

GrsnKe GenJs (Igneous Rock type)

G ~ ~ ( l o n e 0 u s Rocktype)

~ ~ d ~ m ~ (KM.1

394n 37916

Cft R

R

T & I W (Km.)

14.5.20.5

10.4

19.8

22.2

W.1.r

(x)

0.15

0.78

2.818

2.88

Soundmu (54)

I .M

0.8

Oblpping Value(%)

1&20

5-10

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Location Details

Final Detailed Project Report Contract Package - NS 82 (TN)

6 Volume Ill: Material Report Chapter - I : Material Investigations

Chapter Z : Subgrade Investigations

lolnt ventwe wlm BCEOM :, r x m dsscNa~es 4 /6 Laning of K a ~ r - Madurai Section of NH-7 , -- k JJ =---31-ruz-,r?rs r r h-rm Consultancy Services for Feasibility study and Preparation of DPR 1 13 cw*m-Oap

2.0 SUBGRADE INVESTIGATIONS

2.1 INTRODUCTION

The Ministry of Road Transport and Highways (MoRT&H), Govt. of lndia has taken up the development of various National Highway Corridors where the traffic intensity has increased significantly thereby necessitating capacity augmentation for safe and efficient movement of traffic. This Project is a part of North - South corridor connecting Srinagar in J8K State to Kanyakumari in Tamil Nadu. National Highways Authority of lndia (NHAI) has been entrusted to implement the development projects for these corridors. The work of conducting Feasibility Studies and Preparation of Detailed Project Report for Four I Six laning from Karur (Km 305.800) to Madurai (Km. 426.660), a section of NH 7 has been entrusted to the Joint Venture of BCEOM - Aarvee Associates.

For the convenience in construction, the present project conidor has been divided into three packages. They are:

Package NS-80 (TN): Km 305.800 to Km 345.000 Package NS-81 (TN): Km 345.000 to Km 381.200 Package NS-82 (TN): Km 381.200 to Km 426.660

In this chapter, the data pertaining to the Construction package: NS-82 (TN) is presented.

2.2 PROJECT DESCRIPTION

The road section from Km 381.200 to Km 426.660 of NH-7 Package NS-82 (TN) is taken up for conducting detailed engineering studies for rehabilitation and up-gradation of existing 2 lane to 4 lane divided carriage way highway with improved traffic capacity. Soils and material investigation for a road project is an essential requirement to assess real scenario for design and construction. During design stage, the road pavement, embankment, and other structures, the existing soils and materials inventory is needed for their characteristics, availability in right quality and quantity for constructions at reasonable cost. The investigations covered all relevant aspects.

All relevant information such as geological maps data published by various authorities regarding soil profile, ground water quality etc., have been studied to the extent possible. Subgrade investigations along the alignment of the project was essentially directed towards collecting all the data about the existing pavement, subgrade etc., necessary for strengthening the existing pavement for widening and paved shoulders and for new bypass alignments.

The investigation and testing of materials is carried out in accordance with the provisions of TOR clause 4.1 1.3.3.

Final Detailed Project Report Part - 2: Report on Subgrade Investigations I of 12 Contract Package - NS82 (TN) Volume Ill: Material Report

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2.3 SUBGRADE SOIL INVESTIGATIONS

Subgrade investigations along the alignment of the project was essentially directed towards collecting all the data about the existing pavement, subgrade etc., necessary for strengthening the existing pavement for widening and paved shoulders and for new bypass alignments.

2.3.1 Methodology

All relevant information such as geological maps data published by various authorities regarding soil profile, ground water quality etc and data available with PWD (NH) have been studied to the extent possible. In addition fresh investigations were carried out by cutting trial pits in the following manner.

Large test pits (1.0m x 1.0m) were excavated at the pavement - shoulder interface to a depth of 1 m, Minimum three pits were dug for each homogeneous road segment or change of soil as per TOR and staggered IeWright for carrying out the following activities.

9 Measuring and logging the thickness of various pavement layers. 9 Conducting field (in-situ) density test using sand replacement method as per 18:2720 part-28 > Field moisture content 9 Conducting DCP Test (TRL Method) down to a depth of 1.5m below subgrade level. 9 Collecting samples of subgrade (approx. 50Kg) for following laboratory tests

s Atterberg limits As per 18:2720 3 Grain size analysis As per 18:2720 3 Maximum laboratory As per 18:2720

Dry density (heavy compaction) s Optimum Moisture content As per 18:2720 3 CBR (4 days soaked) at AASHTO TI93

three energy levels 3 Free swell index As per lS:2720

9 Collecting Auger samples at different depths for Laboratory tests for soil classification

Small pits (0.7m x 0.7m) were dug upto the subgrade level at the pavement - shoulder interface staggered left/right in between the large pits at every Ikm interval. The following activities were carried out

> Measuring and logging the thickness of various pavement layers 9 Collecting samples of subgrade for following laboratory tests

3 Atterberg limits, 3 Grain size analysis 3 Natural moisture content a Free swell index

New Alignment: Pits on natural ground adjoining the existing pavement to strength for new carriageway1 proposed bypass alignments at every 5Km i following activities were carried out.

\ u< 9 Collecting bulk samples (approx. 50Kg) for following laboratory test. \!a:Y'

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3 Atterberg Limits Grain size analysis

3 Maximum Laboratory dry density (heavy compaction)

3 Optimum moisture content

s CBR (4 days soaked) at three energy levels

3 Free swell index 9 Driving auger down to 1.5m below the natural ground or till hard strata is encountered, 9 collecting 1 Kg sample at I .Om and 1.5117 depth for soil classification 9 Recording water table, If encountered in the bore.

2.3.2 Results of Investigations

The results of field and laboratory investigations have been compiled in the form of tables and are given in the Appendix, at the end of this chapter.

Table 2.1 Test results at Subgrade level at every 1 km interval from small pits

Table 2.2 DCP-CBR value at Sub-grade and below sub-grade level

Table 2.3 Test results at Subgrade and below sub-grade level from large pits

Table 2.4 Test results of natural ground

2.3.3 Field Tests on Existing Alignment

2.3.3.1 Existing Sub-grade

The existing sub-grade soils have been investigated for moisture content, density, DCP-CBR etc. The test was done staggered at the junction of shoulder and carriageway through test pit dug up to the formation level as per standard procedure.

2.3.3.2 Dynamic Cone penetration Test: (TRRL Method)

Dynamic Cone Penetration test according to TRL method was conducted to assess the in-situ CBR at and below subgrade level. The test was conducted at large pits along the existing pavement edge (300 mm from the edge of the carriageway) of the road. TRRL's DCP apparatus consists of a hardened steel cone (60°cone) 20 mm in diameter, which is driven by a weight of 8 Kg with a drop height of 575 mm. The CBR value was calculated for different soil layers encountered from the graph of penetration versus number of blows. Slope changes of penetration versus number of blows graph indicates interface of two soil layers. From this graph, layer thickness and respective slopes (penetration 1 blow) have been calculated.

DCP-CBR value have been calculated using the following formula (TRL overseas using 60" cone)

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Loglo CBR = 2.48 - I .057*loglo (mmlblow)

The above DCP-CBR value was converted to an overall equivalent DCP - CBR value using the following Japanese formula.

Overall CBR = [@(Layer thickness) x (DCP - CBR)'") I (Z(Layer thickness)13

Table 2.2 of Appendix gives the data on the overall CBR. Maximum, minimum and average values of DCP-CBR value have been found to be 71.8, 30.9 and 48.6 respectively.

2.3.3.3 Laboratory test results o f the existing sub-grade

Laboratory test results obtained from small pits have been grouped along with results of large pits and analyzed. The soil samples have been primarily classified on the basis of Bureau of Indian Standards (BIS) which is based on the unified soil classification System (UCS). Density- moisture relation, CBR (soaked) swell at 10, 30 and 65 blows, were determined. Comprehensive results of laboratory tests on subgrade samples of the existing pavement are summarized in Table 2.1 & 2.3 in Appendix. The subgrade soil is mostly sand, sandy clay and some gravel material, with low plasticity. The soil is mostly classified as SM or SC group according to the UCS System. Soil profiles along the alignment have been Fig 2.1 Soil Classification given in Figure 2.6, Appendix.

Soil Classification

SM 27

C 73%

Grain size analysis: In the entire section soil, the 75 micron passing material is 33% (average value) which ranges from 3.4% to 59.9%. Atterberg's Limits: The mean Liquid limit and Plastic limit values are found to be 30% and 15% respectively. The average value of plasticity index of the soil is found to be 15%. About 9% of soil samples have a PI value in the range of 0-1 0%, 51% of soil samples have PI in the range of 10-20%, about 13% of samples have PI in the range of 20-30% and 27% of samples are non-plastic in nature, and is given in the figure 2.2. Moisture content vs. Dry Density relationship (Heavy compaction), is given in the figure 2.4 Soil samples obtained from trial pits have

been compacted in the laboratory at

Plasticity lndex

NP 0-1 0

.1&20

20 13% 51 %

Fia 2.2 Plasticitv lndex

various moisture contents to derive a dry density versus moisture content relationship. The method of heavy compaction in accordance with IS: 2720 (P given in figure 2.3.

Final Detailed Project Report Part - 2: Report on Subgrade lnves Contract Package - NS82 (TN) Volume Ill: Material Report

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It shows Subgrade soil having maximum dry density (MDD) ranging from 1.82 gmlcc to 2.2 gmlcc. The optimum moisture content (OMC) varies from 9.5% to 16.5% showing an average of 12.17%.

FDD & MDD

2 5

3

1': & 0 5

0

l t i i f { f a E f Chaln.0.

Comprehensive results of laboratory 'investigations are tabulated in Table 2.3 of Appendix. The soaked CBR at MDD ranges from 9.6% to 27.7% and the soaked CBR at FDD ranges from 4.6% to 18.5%. Figure 2.5 presents the results of soaked CBR compacted at 97% MDD.

California Bearing Ratio (CBR) tests were carried out Fig 2.3 FDD 8 MDD

on the pit samples as per standard procedures. At OMC, the soil samples were compacted at three different energy levels corresponding to 10 blows, 30 blows and 65 blows as per 18:2720 (Part8). The samples were tested after immersion in water and soaking for four days. The amount of swell, soaked moisture and density were determined for the samples. For the same samples CBR at FDD, 95% of MDD, 97% of MDD and at MDD has been interpolated from the

FMC 8 OMC

m - .-- -

01.1,"'p

results at different levels of compaction.

Fig 2.4 FMC 8 OMC

--

The field dry density and moisture content of the subgrade soil has been measured at every large pit and the results are illustrated in Table C8 of Appendix- C. It shows a range of FDD from 18.0kNl m3 having an average value of 20.0kNI m3. The field moisture content (FMC) varies from 2.0% to 6.1% having an average value of 4.1 %. The average ratio of FMC and OMC is 0.34 while the ratio of FDD and MDD is 0.92.

Investigation of natural ground Fin 2.5 Soaked CBR at 97%

CBR (%)

30 - - - ---- -- - - - - - - -- - -- 25 -

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abutting the existing carriageway and along proposed alignment of bypasses was done through test pit and auger samples collected for Laboratory tests. Comprehensive results of laboratory tests are presented in Table 2.4 of Appendix.

Grain size analysis : Results of Grain size indicates an average value of 75 micron down material is 33% (Range 3.4 % to 59.9%) Atterberg's Limits: The mean Liquid limit and Plastic limit values are found to be 30% and 15% respectively. The average value of plasticity index of the soil is found to be 15% (Range 8% to 25%) Moisture content vs. Dry Density relationship (Heavy compaction) a Average Maximum dry density (MDD) of the natural ground is 2.0glcc (Range: 1.8glcc to 2.

2gmlcc). The optimum moisture content (OMC) varies from 9.5% to 16.5% &owing an average of 12.2%.

CBR Test: Laboratory CBR on the test pit sample from natural ground at MDD has been found to be 18.4% (average value) with a range of 9.6% to 27.7%. Auger Samples: Auger samples were collected at three depth 50cm, Im, 1.5m for natural moisture content. The soil samples from different depths were collected at each site and representative test samples were prepared for analysis.

2.3.3.4 Interpretation of Test Results

Majority of the alignment soil is mostly sand, sandy clay and some gravel material, with low plasticity. The soil is mostly classified as SM or SC group according to UCS system.

Existing Subgrade

In-situ average DCP-CBR value is 48.6% with large variation (Range: 30.9% to 71.8%) which is more than Laboratory CBR 18.4% (Range: 9.6% to 27.7%). This indicates the densification of sub-grade has occurred over a period of time.

Average Optimum Moisture Content (OMC) is 12.2% where as Natural Moisture Content (NMC) is about 6.3%. Therefore the mean NMC is 50% less than OMC.

New Sub-grade1Natural ground

Majority of the natural soil abutting existing alignment is predominantly sandy claylsandy silt (SCISM group) and average Laboratory CBR 13.47% (Range 5% to 23%) which is less than existing subgrade CBR at MDD (20.23%). Average Optimum Moisture Content (OMC) is 12% where as Natural Moisture Content (NMC) at a depth of 0.50m, I m and 2m below ground level was collected and presented in Table 2.4, Appendix.

2.4 RECOMMENDATIONS

Geotechnical lnvestigations including subsurface drilling at the locations of of the various bridges and flyoverslRoBs, insitu testing and laboratory testing during April 2004 to June 2004 through a geotechnical consultant.

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The subsoil investigation work was carried conforming to the requirements of the relevant IS and IRC codes and specifications. The boreholes were advanced using rotary type drilling, SPT values were recorded in the soil formation at on interval of 1.5m generally. Where rock formations were met with, cores were recovered using double tube core barrel. Since formation was sandy soil followed by weathered rock or rock, all through the alignment, it was found possible to adopt open foundations. The depth of foundation was mostly in the range of 2 to 3m and a safe bearing capacity of 30-45 Urn2 was adopted. In a few cases foundation depth was deeper. In case of lightly loaded structures, foundation were located on sandy layers and allowable bearing capacity of 15 to 25 Um2 was adopted.

Basic input for the design of pavements is the soaked CBR value compacted at 97% MDD. Considering this parameter, and the type of existing soils available, a soaked CBR value of 10% has been adopted uniformly for the design of existing and new pavement.

In order to evaluate the stability of high embankments in the approaches to bridge and other structures, two bore holes were drilled in each of the approaches as well as the strength properties of fill soils were evaluated. The sub-soils in the stretch are materials having high shear strength as also the fill materials. The high embankments are safe with 1:2 side slopes.

Final Detailed Project Report Part - 2: Report on Subgrade Investigations 7 of 12 Contract Package - NS82 (TN) Volume Ill: Material Report

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Table 2.1 : Summary of Test Results Laboratory test results of Subgrade soil samples at small pits

Final Detailed Project Report Contraa Package- NS82 (TN) Volume Ill : Material Report Chapter - 2 : Subgrade Investigation 80f 12

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Final Detailed Pmject Report Contracl Package- NS82 (TNJ Volume Ill : Material Report

Table 2.2 : Results of CBR &SNSG from DCP Tests

Chapter - 2 : Subgrade Investigation

NO.

Overall CBR

Japanese 1 SNSG

Test location (h)

Layer 1

NO. of DCP- I blows I CBR

Layer3 No. Of OCP- 1 blows I CBR

Layer2

Thickness NO. of DCP-

CBR

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Table 2.3 : Summaty of Test Results

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