thesis in m.tech

A STUDY ON INFLUENCE OF SOAKING ON CBR VALUE OF SOIL

A Thesis

Submitted in partial fulfillment for the requirement of the degree

of

MASTER OF TECHNOLOGY

in

TRANSPORTATION ENGINEERING

by

PRIYESH GANGELE

Scholar No.: 082111509

Under the guidance of

Dr. P. K. AGARWAL

Dr. S. ROKADE

DEPARTMENT OF CIVIL ENGINEERINGMAULANA AZAD NATIONAL INSTITUTE OF TECHNOLOGY,

BHOPAL (MP)DECEMBER, 2013

CERTIFICATE

This is to certify that the Thesis titled “A STUDY ON INFLUENCE OF SOAKING

ON CBR VALUE OF SOIL IN STATE OF MADHYA PRADESH” submitted by PRIYESH

GANGELE in partial fulfillment of the requirements for the degree of MASTER OF

TECHNOLOGY in TRANSPORTATION ENGINEERING is a bonafide work carried out by

him under our supervision and guidance.

Dr. S. Rokade Dr. P.K. Agarwal Asst. Professor ProfessorDeptt. of Civil Engineering Deptt. of Civil Engineering M.A.N.I.T., Bhopal M.A.N.I.T., Bhopal

CANDIDATE’S DECLARATION

I hereby declare that the Thesis entitled “A STUDY ON INFLUENCE OF SOAKING

ON CBR VALUE OF SOIL IN STATE OF MADHYA PRADESH” submitted by me in

partial fulfillment of the requirement of the degree of Master of Technology in “Transportation

Engineering” of Maulana Azad National Institute of Technology is an authentic record of my

own work carried out under the guidance of Professor Dr. P.K. Agarwal & Asst. Prof. Dr. S.

Rokade, Department of Civil Engineering M.A.N.I.T. Bhopal. The matter embodied in this

project has not been submitted by me for the award of any other degree or diploma.

(PRIYESH GANGELE)

ACKNOWLEDGEMENT

I express my deep sense of gratitude I am also thankful to Professor Dr. P.K. Agarwal, Deptt. of

Civil Engineering, Maulana Azad National Institute of Technology, Bhopal for his invaluable help

and guidance. I am highly thankful to him for his continuous support and encouragement in

completing this work. I am also thankful to Asst. Prof. S. Rokade Deptt. of Civil Engineering,

Maulana Azad National Institute of Technology, Bhopal.

I am thankful to Dr. Appu Kuttan K.K., Director, Maulana Azad National Institute of

Technology, Bhopal and Professor Dr. V. Prasad Head of Department, Deptt. of Civil Engineering,

Maulana Azad National Institute of Technology, Bhopal for their continuous support and

encouragement in completing my M.Tech programme. I am also grateful to Dr. Ganga Agnihotri

Dean, Academics, for his guidance and immortal support.

Special thanks to Professor Dr. S. K. Katiyar, Deptt. of Civil Engineering, Maulana Azad

National Institute of Technology, Bhopal for their guidance and support during my Post Graduation

Programme.

Thanks is also extended to Mr. Ramanuj Yadav, Lab Assistant and Mr. Mahesh Verma,

Office Assistant, Deptt. of Civil Engineering, Maulana Azad National Institute of Technology,

Bhopal. I also express deep sense of appreciation to the staff of Deptt. of Civil Engineering, Maulana

Azad National Institute of Technology, Bhopal for their cooperation and support throughout the

session.

I am thankful to my friends Rakesh Mehar, Er. Shashank Tiwari, Er. Rahul Sahu, and

other well wishers whose names could not mentioned but without their direct or indirect contribution

this thesis would never been a success.

Last but not the least; my heartiest thanks to my Parents and my brother and my sister for their

blessings, keen interest, active support and pains taken by them during the entire duration of my

studies.

BHOPAL December 2013 PRIYESH GANGELE

2.4 IRC RECOMMENDATIONS FOR THE CBR METHOD OF DESIGN

16

CONTENTS

TITLES PAGE NO

CERTIFICATE

DECLARATION

ACKNOWLEDGEMENT

ABSTRACT 01

LIST OF TABLE 02

LIST OF FIGURES 03 - 04

CHAPTER 1. INTRODUCTION 05

1.1 NEED OF STUDY 06

1.2 OBJECTIVE & SCOPE OF STUDY 07

1.3 THESIS ORGANISATION 08

CHAPTER 2. LITERATURE REVIEW 09

2.1 IMPORTANCE OF CBR OF SOIL SUBGRADE 10 - 11

2.2 DETERMINATION OF CBR VALUE OF SOIL SUBGRADE 12 - 15

2.3 QUICK ESTIMATION OF CBR 15

2.5 TYPICAL PREASUMPTIVE VALUE OF CBR 17

CHAPTER 3. DETAILS OF LABORATORY STUDIES 18

3.1 CALIFORNIA BEARING RATIO (The actual laboratory method) 19-20

3.2 DETERMINATION OF INDEX PROPERTY 21

3.2.1 LIQUID LIMIT TEST 21

3.2.2 PLASTIC LIMIT TEST 21

3.3 DETERMINATION OF CBR OF SOIL 21

CHAPTER 4. ANALYSIS & RESULTS 22

4.1 ANALYSIS & RESULT OF SAMPLE NO. 1 23-31




CHAPTER 5. CONCLUSIONS & RECOMMANDATION FOR FURTHER STUDY

59

5.1 CONCLUSION59

5.2 RECOMMANDATION FOR FUTHER STUDY 59-60

REFERENCES61-62

Pavements are a conglomeration of materials. These materials, their associated

properties, and their interactions determine the properties of the resultant pavement. Thus, a good

understanding of these materials, how they are characterized, and how they perform is

fundamental to understanding pavement. The materials which are used in the construction of

highway are of intense interest to the highway engineer. This requires not only a thorough

understanding of the soil and aggregate properties which affect pavement stability and durability,

but also the binding materials which may be added to improve these pavement features. Soil is

an accumulation or deposit of earth material, derived naturally from the disintegration of rocks or

decay of vegetation, that can be excavated readily with power equipment in the field or

disintegrated by gentle mechanical means in the laboratory. The supporting soil beneath

pavement and its special under courses is called sub grade. Undisturbed soil beneath the

pavement is called natural sub grade. Compacted sub grade is the soil compacted by controlled

movement of heavy compactors. The performance of pavements depends to a large extent on the

strength and stiffness of the subgrade. Among the various methods of evaluating the subgrade

strength, CBR test is important but quick estimate of CBR is very important for highway

engineer so this study is focus on compression of soaked and unsoaked CBR value.

This Study is an attempt to understand the influence of soaking on CBR

value subjected to different days of soaking and the corresponding variation

in moisture content. It is observed that the CBR decreases and the moisture

content increases for high degree of soaking.

ABSTRACT

Table No. Description Page No.

Table 1 Standard Crushes Rock from California Value 11

Table 2 Standard Load Values 14

Table 3 Typical presumptive CBR values 17

Table 4 Analysis & Result of Sample No. 1 23

Table 5 Grain Size Analysis of Sample No. 1 24

Table 6 Analysis of Sample No. 2 32






Table 12 Variation of CBR with time of soaking of sample no 1 to 4

LIST OF TABLE

Fig. No. Description Page No.

Fig. 1 CBR Apparatus 12

Fig. 2 LL & PL Test Result of sample no. 1 25

Fig. 3 CBR Test Result (0 Hrs.) of sample no. 1 26

Fig. 4 CBR Test Result (24Hrs.) of sample no. 1 27



Fig. 7 CBR Analysis Result (96 hrs.) of sample no. 1 30

Fig. 8 Variation of CBR with time of soaking sample no. 1 31







Fig. 15 Variation of CBR with time of Soaking Sample No. 2 40

LIST OF FIGURES















Fig. 30 Variation of CBR with time of soaking of sample no 1 to 4 60

CHAPTER-1INTRODUCTION

CHAPTER -1

INTRODUCTION

1.1 Need of study

Damages of roads by floods are common phenomena in MP and a huge Expenditure is

required almost after each flood for rehabilitation of the roads. Therefore, research aiming at

finding the modes of damages to roads under flood has become necessary. Several factors may

appear to be responsible for such damages, which need to be confirmed by experiments. This

study aimed at determining the effects of depth of submergence and duration of submergence on

the sub grade strength of soil samples collected from the sagar-Chhatarpur National

Highway .CBR tests were performed with different heights of submergence after normal soaking

period and also after prolonged submergence. Index and identification tests were performed for

classification and for determination of the suitability of the studied soils as subgrade material.

However, it was observed that all the three types of soils tested are rated as poor materials for

subgrade according to IS soil classification systems.

Design of the various pavement layers is very much dependent on the strength of the

subgrade soil over which they are going to be laid. Subgrade strength is mostly expressed in

terms of CBR (California Bearing Ratio). Weaker subgrade essentially requires thicker layers

whereas stronger subgrade goes well with thinner pavement layers. The pavement and the

subgrade mutually must sustain the traffic volume. The Indian Road Congress (IRC) encodes the

exact design strategies of the pavement layers based upon the subgrade strength which is

primarily dependant on CBR value for a laboratory or field sample soaked for four days. The

subgrade is always subjected to change in its moisture content due to rainfall, capillary action,

overflow or rise of water table. For an engineer, it's important to understand the change of

subgrade strength due to variation of moisture content. This project is an attempt to understand

the influence of soaking on CBR value subjected to different days of soaking and the

corresponding variation in moisture content. It is observed that the CBR decreases and the

moisture content increases for high degree of soaking.

1.2 Objective & Scope of Study

It is common in the state of MP that the sub grade strength for highway pavement design is

determined by CBR test measurement. This can be from the laboratory CBR test or directly from

field CBR test. The correlation between the result of CBR soaked test and CBR soaked value is

hardly found. This Thesis objective is to obtain a local correlation between the results of CBR

laboratory test without soaked and CBR soaked value. The correlation is based on the

comparison CBR unsoaked test results and CBR soaked value which has the same fraction of

sand and clay in soil.

In MP, California Bearing Ratio (CBR) value of sub grade is used often for design of

flexible pavements. In practice, only limited number of such tests could be performed because of

high unit cost and time required for such testing. As a result, in many cases, it is difficult to

reveal detailed variations in the CBR values, over the length of roads. In such cases if the

estimation of the CBR could be done on the basis of some tests which are quick to perform, less

time consuming and cheap, then it will be easy to get the information about the strength of

subgrade over the length of roads and also will be helpful and important specially for low

volume roads being different states of India presently, to develop large scale connections of rural

India within a short period of time. By considering this aspect, a number of investigators in the

past made their investigations in this field and developed different methods for determining the

CBR value on the basis of results of low cost, less time consuming and easy to perform tests. In

this thesis, attempts have been made to seek the validation of the predicted values of CBR

determined by different method as per guidelines of IRC: SP: 72-2007.

The present scope of work for this thesis is to ascertain the CBR value under different

soaking time conditions and to study the influence ,in the samples under varying soaking.

1) To collect a particular soil sample and determine its basic physical property such

as LL,PL,PI and grain size distribution

2) To study the soil under modified proctor compaction and determine the MDD and

OMC for the soil sample

3) To carry out CBR Test for sample soaked in different times

4) To study the influence of soaking on subgrade strength

1.3 Thesis Organization

In Chapter 1 represent Introduction, In Chapter 2 represent Literature Review, In Chapter 3

represent Details of Laboratory Studies, In Chapter 4 represent Analysis & Results, In Chapter 5

represent Conclusions & Recommendation for Further Study.

CHAPTER – 2LITERATURE REVIEW

CHAPTER -2

LITERATURE REVIEW

2.1 Importance of CBR of Soil Subgrade

The load bearing capacity of the soil supporting highways, airfield runways and other

pavement systems is of immense importance to the integrity of the pavement. This load-bearing

capacity, or soil stiffness, changes from time to time and can vary from place to place within a

given area.

Soil stiffness is the degree of resistance to deformation upon loading. The extent and

time-dependence of, and the degree of recovery from, deformation is primarily dependent upon

the soil's properties, existing stress conditions, and the stress history. Soil properties in turn are

determined by a variety of complex interrelated factors, including composition particle size and

particle-size distribution, weight-volume relationships, and in-situ stresses. The stability or load-

bearing capacity (capability) of the pavement of airport runways, highways and other pavement

systems is determined in significant part by the load-bearing capacity of the underlying sub

pavement) earth or soil, which may deteriorate over time due to environmental and stress

influences on soil properties. For instance, changes in soil load-bearing conditions due to

changes in moisture content and/or repeated loading over time are well recognized in

engineering fields. In addition, certain pavement systems such as runways and highways

typically endure repeated severe loadings on a daily basis.

The proper determination of existing bearing-load capacities of soil-supported pavement

systems requires that the existing soil conditions be defined and evaluated. Conventional soil-

structure modeling is based on the results of laboratory testing of individual localized soil

samples, as in the case of the well-known California Bearing Ratio, or CBR, laboratory test.

However, tests such as the CBR are severely disadvantaged because the test conditions and the

soil sample (specimen) are not representative of in-situ conditions. Absent are (a) in-situ

overburden stress, (b) in-situ soil interactions, and the like. Further, many if not most soil

samples have been disturbed to some degree during sampling and handling. A true composite

soil stiffness determination can only be determined using actual stiffness data of in-situ soil

conditions at varying depths (varying subgrade conditions).

Another known method for determining composite soil stiffness is the use of plate

bearing tests on the surface of soil layers. As mentioned herein above, the current most widely

used way to determine soil stiffness is by using the California Bearing Ratio (CBR) test on soil

samples that are prepared in the laboratory, the objective being to calculate with the stiffness, or

resilient modulus of soil. As per MORT&H Specifications, subgrade can be defined as a

compacted layer, generally of naturally occurring local soil, assumed to be 300 mm in thickness,

just beneath the pavement crust, providing a suitable foundation for the pavement. The subgrade

in embankment is compacted in two layers, usually to a higher standard than the lower part of the

embankment. In cuttings, the cut formation, which serves as the subgrade, is treated similarly to

provide a suitable foundation for the pavement.

Where the naturally occurring local subgrade soils have poor engineering properties and

low strength in terms of CBR, for example in Black Cotton soil areas, improved subgrades are

provided by way of lime/cement treatment or by mechanical stabilization and other similar

techniques.

The California Bearing Ratio test is to determine the CBR value for a soil under

consideration as a pavement foundation. This value is a percentage comparison with the

standard crushed rock from California. Thus this test is a comparison test. The CBR value is

used to quantify the response of the pavement foundation and subgrade to loading.

The standard crushes rock from California values are as follows:

Table No. 1 (Standard crushes rock from California value)

Load (kN)

13.24 19.96

Penetration (mm)

2.5 5.0

It should be noted that this test was created by the California Division of Highways in the 1930’s and as such is an empirical test and does not provide any data regarding properties of the soil except as to compare its resistance to penetration to the base crushed rock’s resistance to penetration.

The test remains in existence around the world due to its low equipment requirements, easy of performance and history of use.

It is important to realize that the CBR test is but one step in the road pavement foundation design process; the test allows the road Engineer to design the capping layer (if needed) and the sub-base Layer by determining the strength of the underlying soil.

By knowing this the Engineer can determine if this strength is adequate to handle the desired road design or if additional procedures need to be done to increase this strength.

2.2 Determination of CBR Value of Soil Subgrade

Apparatus:

1. Loading machine-any compression machine can operate at constant rate of 1.25mm per

minute can be used.

2. Cylindrical moulds- moulds of 150mm diameter and 175mm height provided with a collar of

about 50mm length and detachable perforated base.

3. Compaction rammer,

4. Surcharge weight-annular weights each of 2.5kg and 147mm diameter.

5. IS sieve 19mm, coarse filter paper, balance etc.

Fig. No. 1 (CBR Apparatus)

The California Bearing Ratio(CBR) test was developed by the California Division of

Highways as a method of classifying and evaluating soil- subgrade and base course materials for

flexible pavements. CBR is a measure of resistance of a material to penetration of standard

plunger under controlled density and moisture conditions. CBR test may be conducted in

remolded or undisturbed sample. Test consists of causing a cylindrical plunger of 50mm

diameter to penetrate a pavement component material at 1.25mm/minute. The loads for 2.5mm

and 5mm are recorded. This load is expressed as a percentage of standard load value at a

respective deformation level to obtain CBR value.

Sieve the sample through 19 mm IS sieve. Take 5kg of the sample of soil specimen. Add

water to the soil in the quantity such that optimum moisture content or field moisture content is

reached. Then soil and water are mixed thoroughly. Spacer disc is placed over the base plate at

the bottom of mould and a coarse filter paper is placed over the spacer disc. The prepared soil

water mix is divided into five. The mould is cleaned and oil is applied. Then fill one fifth of the

mould with the prepared soil. That layer is compacted by giving 56 evenly distributed blows

using a hammer of weight 4.89kg. The top layer of the compacted soil is scratched. Again

second layer is filled and process is repeated. After 3rd layer, collar is also attached to the mould

and process is continued. After fifth layer collar is removed and excess soil is struck off. Remove

base plate and invert the mould. Then it is clamped to base plate.

Surcharge weights of 2.5kg are placed on top surface of soil. Mould containing specimen

is placed in position on the testing machine. The penetration plunger is brought in contact with

the soil and a load of 4kg (seating load) is applied so that contact between soil and plunger is

established. Then dial readings are adjusted to zero. Load is applied such that penetration rate is

1.25mm per minute. Load at penetration of 0.5, 1, 1.5, 2, 2.5, 3,4,5,7.5,10 and 12.5mm are noted.

Standard Load Values

Table No. 2 (Standard Load Value)

Penetration(mm) Standard Load(kg)Unit Standard Load(kg/cm2)

2.5 1370 70

5 2055 105

7.5 2630 134

10.0 3180 162

12.5 3600 183

Result:

California Bearing Ratio at 2.5mm penetration =

California Bearing Ratio at 5.0mm penetration =

. For the pavement design of new roads the subgrade strength needs to be evaluated in

terms of CBR value which can be estimated by any of the following methods:

1. Based on soil classification tests and the table given in IRC:SP:72-2007 which gives typical

presumptive design CBR values for soil samples compacted to proctor density at optimum

moisture content and soaked under water for 4 days.

2. Using a Nomo graph based on wet sieve analysis data, for estimating 4-day soaked CBR

values on samples compacted to proctor density.

3. Using two sets of equations, based on classification test data, one for plastic soils and the

other for non-plastic soils, for estimating soaked CBR values on samples compacted to

proctor density.

4. By conducting actual CBR tests in the laboratory.

The third and forth method come in handy where adequate testing facilities are not available

or

the project is of such a size as to not to warrant elaborate testing procedures

2.3 Quick Estimation of CBR

1. Plastic soil

CBR= 75/(1+0.728 WPI),

Where WPI= weighted plasticity index= P0.075× PI= Plasticity index of soil in %

P0.075= % Passing 0.075 mm sieve in decimal

2. Non- Plastic soil

CBR= 28.091(D60)0.3581

Where

D60= Diameter in mm of the grain size corresponding to 60% finer.

Soil classification can be used for preliminary report preparation.

2.4 IRC Recommendations for the CBR Method of Design

Some of the important points recommended by IRC for the CBR method of design

(IRC:37 – 1970) are given below:

The CBR tests should be performed on remoulded soils in the laboratory. In – Site tests are

not recommended for design purpose. The specimens should be prepared by static

compaction where ever possible and other wise by dynamic compaction. The standard test

procedure should be strictly adhered to.

For the design of new roads the sub grade soil sample should be compacted at OMC to

proctor density whenever suitable compaction equipment is available to achieve this density

in the fields; otherwise the soil sample may be compacted to the dry density.

expected to be achieved in the field. In the case of existing roads, the sample should be compacted to

field density of sub graded soil (at OMC or at a field moisture content.)

In new constructions the CBR test samples may be soaked in water for four days period

before testing. However in areas with arid climate or when the annual rain fall is less than 50

cm and the water table is too deep to affect the sub grade adversely and when thick and

impermeable bituminous surfacing is provided, it is not necessary to soak the soil specimen

before carrying out the CBR test. Wherever possible the most adverse moisture condition of

the sub grade should be determined from the field study.

At least three samples should be tested on each 1 type of soil at the same density and

moisture content. If the maximum variation in CBR valves of the three specimens exceeds

the specified limits, the design CBR should be the average of at least six samples ( The

specified limits of maximum variation in CBR are 3 for CBR values up to 10,5 for values 10

to 30 and 10 for values 30 to 60%)

The top 50-cm of sub grad should be compacted at least up to 95 to 100 percent of proctor

density.

An estimate of the traffic to be carried by the road pavement at the end of expected life

should be made keeping in view the existing traffic and probable growth in traffic due to

change in the land use. Pavements of major roads should be designed at least for 10days life

period and the following formula may be used in such cases for traffic prediction.

Where

A = Number of heavy vehicles per day for design (laden Weight>3 tonnes)

P = number of heavy vehicles per day at least count

r = annual rate of increase of heavy vehicles.

n = number of years between the last count and the year of completion of construction.

A = P (1+r)(n+10).

The value of P in the formula should be the seven day average of heavy vehicles found from

24 hour counts. If a reliable value of growth factor r is not available, a value of 7.5% may be

assumed for roads in rural areas.

The traffic for the design is considered in units of heavy vehicles (of laden weight exceeding

3 tons) per day in both directions and are divided into seven categories A to G. The suitable

design curve should be chosen from the table given in the design chart (fig). The design

thickness is considered for single axle loads upto 8,200 kg and random axle loads upto

14,500 kg. For higher axle loads the thickness values should be further increased.

(This is improvement over earlier mentioned values of 8160 kg and 4080 kg)

When sub-base course materials contain substantial proportion of aggregates of size above

20 mm, the CBR value of these materials would not be valid for the design of subsequent

layers above them. This layers of wearing course such as surface dressing or open graded

premixed carpet up to 2.5 cm thickness should not be counted towards the total thickness of

pavement as they do not increase the structural capacity as the pavement.

2.5 Typical Presumptive Value of CBR

Table- 3 Typical presumptive CBR values

CBR VALUE SUBGRADE STRENGTH

3% or less Poor

3% - 5% normal

5% - 15% good

CHAPTER – 3DETAILS OF LABORATORY

STUDIES

CHAPTER -3

DETAILS OF LABORATORY STUDIES

3.1 California Bearing Ratio (The actual laboratory method)

The CBR test was originally developed by O.J. Porter for the California Highway

Department during the 1920s. It is a load-deformation test performed in the laboratory or the

field, whose results are then used with an empirical design chart to determine the thickness of

flexible pavement, base, and other layers for a given vehicle loading. Though the test originated

in California, the California Department of Transportation and most other highway agencies

have

Since abandoned the CBR method of pavement design. In the 1940s, the US Army Corps

of Engineers (USACE) adopted the CBR method of design for flexible airfield pavements.

The thickness of different elements comprising a pavement is determined by CBR values.

The CBR test is a small scale penetration test in which a cylindrical plunger of 3 in2 (5 cm in

dia) cross-section is penetrated into a soil mass (i.e., sub-grade material) at the rate of 0.05 in. per

minute (1.25 mm/minute). Observations are taken between the penetration resistance (called the

test load) versus the penetration of plunger. The penetration resistance of the plunger into a

standard sample of crushed stone for the corresponding penetration is called standard load. The

California bearing ratio, abbreviated as CBR is defined as the ratio of the test load to the standard

load, expressed as percentage for a given penetration of the plunger. CBR = (Test load/Standard

load)×100 The table gives the standard loads adopted for different penetrations for the standard

material with a CBR value of 100%.

Four Lot of soil samples of NH86 Bhopal to Chhatarpur Road taken as per classification.

Samples are molded at its optimum moisture content to its proctor density was tested for its

soaked and unsoaked CBR strength and also carried out IS classification as per IS 2720 and wet

sieve analysis also carried out by four soil sample. Thus the process comprises of three parts.

1. On original sample carried out first wet sieve analysis, liquid limit and plastic limit.

2. Estimation of proctor density and optimum moisture content for each soil sample.

3. Molding the soil sample into standard moulds keeping its moisture content and dry density

exactly same as its optimum moisture content and proctor density respectively.

4. Determination of CBR strength of the respective soil samples in moulds using the CBR

instrument.

5. Each soil sample is tested for its soaked CBR and unsoaked CBR strength after being

soaked in water for 4 days

The experimental work comprises in the following parts:

3.2 Determination Of Index Property

Liquid limit by liquid limit device

Plastic limit

Plastic Index

Shrinkage limit

3.2.1 Liquid Limit Test

This test is done to determine the liquid limit of soil as per IS: 2720 (Part 5) – 1985. The

liquid limit of fine-grained soil is the water content at which soil behaves practically like a

liquid, but has small shear strength. Its flow closes the groove in just 25 blows in

Casagrande’s liquid limit device.

3.2.2 Plastic Limit Test

Plastic limit is defined as minimum water content at which soil remains in plastic state.

The plasticity index is defined as the numerical difference between its Liquid limit and Plastic

limit.

3.3 Determination of CBR of Soil

(i) Moulding the soil sample into standard moulds keeping its moisture content and dry

density exactly same as its optimum moisture content and proctor density respectively.

(ii) Determination of CBR strength of the respective soil samples in moulds using the CBR

instrument.

(iii) Soil sample is tested for its CBR strength after being soaked in water for 1 day, 2 days, 3

days and 4 days. Unsoaked CBR is also determined for each sample.

CHAPTER – 4ANALYSIS & RESULTS

CHAPTER - 4ANALYSIS & RESULTS

FOUR Lot of collected soil samples are moulded at its optimum moisture content to its proctor

density was tested for its soaked and unsoaked CBR strength and also carried out IS Classification.

4.1 ANALYSIS & RESULT OF SAMPLE NO. 1

The result of CBR test of soil sample performed in the laboratory under different

times of soaking are presented in table no. 4

Observation Reports of Sample No. 1 are given below :-

1. Grain Size Analysis

2. Consistency Limit

3. Free Swell Index

4. MDD & OMC

5. CBR Unsoaked

6. CBR Soaked

Table No. 4(Analysis & Result of sample No. 1)

Atterberg’s Limit

CBR Unsoaked(0 Hrs.)

CBR soaked

(24 Hrs.)

CBR soaked

(48 Hrs.)

CBR soaked

(72Hrs.)

CBR with 4

day Soaking

Liquid

Limit (LL)

%

Plastic

Limit (PL) %

Plasticity Index (PI) %

Free Swell Index

Mas Dry

Density gm/cc

OMC%

38.40 20.53 17.87 24.5 1.9 12 18.57 9.66 7.14 6.05 5.02

Table No.5(Grain size analysis of sample no. 1)

Fig. No. 2(LL & PL Test Result of sample no. 1


Fig. No. 3(CBR Test Result (0 Hrs.) of sample no. 1)

Fig. No. 4(CBR Test Result (24Hrs.) of sample no. 1)

Fig. No. 4(CBR Test Result (24Hrs.) of sample no. 1)

Fig. No. 5(CBR Test Result (48 Hrs.) of sample no. 1)

Fig. No. 6(CBR Test Result (72Hrs.) of sample no. 1

CBR with 96 Hrs. Soaking

Sample No. 1


Fig. No. 7

VARIATION OF CBR WITH TIME OF SOAKINGSAMPLE NO. 1

Fig. No. 7

Fig. No. 8


CBR soaked(24 Hrs.)

CBR soaked(48 Hrs.)

CBR soaked(72Hrs.)

CBR with 4 day Soaking

(96 Hrs.)

18.57 9.66 7.14 6.05 5.02

4.2

ANALYSIS & RESULT OF SAMPLE NO. 2



0.0 20.0 40.0 60.0 80.0 100.0 120.00.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

Time in Hour's

C BR

in

%)

Fig. No. 8

Atterberg's Limit

Free Swell Index

Mas Dry

Density gm/cc

OMC%

CBR Unsoake

d(0 Hrs.)

CBR soaked

(24 Hrs.)

CBR soaked

(48 Hrs.)

CBR soaked(72Hrs.

)

CBR with 4

day Soakin

g

Liquid Limit (LL)

%

Plastic Limit

(PL) %


34.50 20.53 13.97 29.25 1.9 12 25.25 13.37 10.40 7.35 6.19




3. Free Swell Index

4. MDD & OMC

5. CBR Unsoaked

6. CBR Soaked

Table No. 6(Analysis of Sample No. 2)

Table No. 7(Grain Size Analysis of sample no. 2

Fig. No. 10(CBR Test Result (0 Hrs.) of sample no. 2

CBR with 96 Hrs. SoakingSample No. 2



CBR soaked(24 Hrs.)

CBR soaked(48 Hrs.)

CBR soaked(72Hrs.)

CBR with 4 day Soaking(96 Hrs.)

25.25 13.37 10.40 7.35 6.19


Fig. No. 15

0.0 20.0 40.0 60.0 80.0 100.0 120.00.00

5.00

10.00

15.00

20.00

25.00

30.00

Time in Hour's

C BR

in

%)




Atterberg's Limit

Free Swell Index

Mas Dry

Density gm/cc

OMC%

CBR Unsoake

d(0 Hrs.)

CBR soaked

(24 Hrs.)

CBR soaked

(48 Hrs.)

CBR soaked(72Hrs.

)

CBR with 4

day Soakin

g

Liquid Limit (LL)

%

Plastic Limit

(PL) %


33.26 20.53 12.73 16.3 1.87 9 21.54 12.63 11.88 10.40 8.37


Fig. No. 15

Table No. 8(Analysis of sample no. 3)



3. Free Swell Index

4. MDD & OMC

5. CBR Unsoaked

6. CBR Soaked

Table No. 9(Grain size analysis of sample no. 3)

Fig. No. 21



CBR soaked(24 Hrs.)

CBR soaked(48 Hrs.)

CBR soaked(72Hrs.)


21.54 12.63 11.88 10.40 8.37

Fig. No. 22(Variation of CBR with time of Soaking Sample No. 3)

0.0 20.0 40.0 60.0 80.0 100.0 120.00.00

5.00

10.00

15.00

20.00

25.00

30.00

Time in Hour's

C BR

in

%)

Fig. No. 21


The result of CBR test of soil sample performed in the laboratory under different times of

soaking are presented in table no. 10

Atterberg's Limit

Free Swell Index

Mas Dry

Density

gm/cc

OMC%

CBR Unsoake

d(0 Hrs.)

CBR soaked

(24 Hrs.)

CBR soaked

(48 Hrs.)

CBR soaked(72Hrs.

)

CBR with 4

day Soakin

g

Liquid Limit (LL)

%

Plastic Limit (PL) %


31.53 20.53 11.00 19.3 1.93 10 17.83 9.66 8.91 7.43 5.31


Table No. 10(Analysis of sample No. 4)



3. Free Swell Index

4. MDD & OMC

5. CBR Unsoaked

6. CBR Soaked

Table No. 11(Grain Size Analysis of sample No 4)

Fig. No. 23

Fig. No. 25


CBR with 96 Hrs. SoakingSample No. 4

VARIATION OF CBR WITH TIME OF SOAKINGSAMPLE NO.4


CBR soaked(24 Hrs.)

CBR soaked(48 Hrs.)

CBR soaked(72Hrs.)


17.83 9.66 8.91 7.43 5.31

0.0 20.0 40.0 60.0 80.0 100.0 120.00.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

Time in Hour's

C BR

in

%)

Fig. No. 29(Variation of CBR with time of Soaking Sample No. 4)

CHAPTER - 5CONCLUSIONS & RECOMMANDATION FOR FUTHER

STUDY

5.1 CONCLUSION

From the results and discussions described earlier, it is observed that the CBR value of the

given soil sample decreases rapidly with time of soaking up to 24 hrs. and then decreases slowly.

When soil samples are taken from different points of the CBR sample and tested

This Study is an attempt to understand the influence of soaking on CBR value subjected to

different days of soaking and the corresponding variation in moisture content. It is observed that the

CBR decreases and the moisture content increases for high degree of soaking.

5.2 RECOMMANDATION FOR FUTHER STUDY

It is recommended that more studies on different type of soil prevailing in studies to be

conducted involving large number of samples.

Table No. 12(Variation of CBR with time of soaking of sample no 1 to 4)

Fig. No. 30(Variation of CBR with time of soaking of sample no 1 to 4)

Sample No.

CBR result (0 Hrs.)

CBR result (24 Hrs.)





1 18.57 9.66 7.14 7.14 6.05 5.02

2 25.25 13.37 10.4 10.4 7.35 6.19

3 21.54 12.63 11.88 11.88 10.4 8.37

4 17.83 9.66 8.91 8.91 7.43 5.31

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Bindra S.P. "A Text Book of Highway Engineering" Dhanpat Rai Publications, New Delhi

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Mathew V. Tom , (2009), Entitled "Pavement materials: Soil Lecture notes in Transportation

Systems Engineering.

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