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 TRANSPORTATION ENGINEERING

by PRIYESH GANGELE

Scholar No.: 082111509 Under the guidance of Dr. P. K. AGARWAL Dr. S. ROKADE

DEPARTMENT OF CIVIL ENGINEERING MAULANA 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 Asst. Professor Deptt. of Civil Engineering M.A.N.I.T., Bhopal

Dr. P.K. Agarwal Professor Deptt. of Civil Engineering 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 m y 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

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

2.4 IRC RECOMMENDATIONS FOR THE CBR METHOD OF DESIGN

16

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


32-39


41-49


50-58

CHAPTER 5. CONCLUSIONS & RECOMMANDATION FOR FURTHER STUDY

5.1 CONCLUSION 5.2 RECOMMANDATION FOR FUTHER STUDY REFERENCES

59

59 59-60 61-62

ABSTRACT 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 exten t 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.

LIST OF TABLE

Table No.

Description

Table 1

Standard Crushes Rock from California Value

Table 2

Standard Load Values

Table 3

Typical presumptive CBR values

Table 4

Analysis & Result of Sample No. 1

Table 5

Grain Size Analysis of Sample No. 1

Table 6

Analysis of Sample No. 2

Table 7


Table 8


Table 9


Table 10


Table 11


Table 12

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

Page No.

11

14

17

23

24

32

33

41

42

50

51

LIST OF FIGURES

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. 5


28

Fig. 6


29

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. 9


34

Fig. 10


35

Fig. 11


36

Fig. 12


37

Fig. 13


38

Fig. 14


39

Fig. 15

Variation of CBR with time of Soaking Sample No. 2

40

Fig. 16


43

Fig. 17


44

Fig. 18


45

Fig. 19


46

Fig. 20


47

Fig. 21


48

Fig. 22


49

Fig. 23


52

Fig. 24


53

Fig. 25


54

Fig. 26


55

Fig. 27


56

Fig. 28


57

Fig. 29


58

Fig. 30

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

60

CHAPTER-1 INTRODUCTION

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 materi als 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 t he 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 su b 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 mad e 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 – 2 LITERATURE 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 o n 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 la yer, 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 sub grade, 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 p ercentage 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)

Penetration (mm)

13.24

2.5

19.96

5.0

It should be noted that this test was created b y 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 ne ed to be done to increase this strength.

2.2 Determination of CBR Value of Soil Subgrade Apparatus: 1. Loading machine-any compression machine can op erate 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 rd

filled and process is repeated. After 3 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)

2

Penetration(mm)

Standard Load(kg)

Unit Standard Load(kg/cm )

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 0.3581

CBR= 28.091(D60) 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.

A = P (1+r)

(n+10)

.

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. 

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 – 3 DETAILS 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 respectivel y.

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 d ensity 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 da ys, 3 days and 4 days. Unsoaked CBR is also determined for each sample.

CHAPTER – 4 ANALYSIS & RESULTS

CHAPTER - 4 ANALYSIS & 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.


The result of CBR test of soil sample performed in the laboratory under different times of soaking are presented in table no. 4

Table No. 4 (Analysis & Result of sample No. 1) Atterberg’s Limit

Liqui d Limit (LL) %

Plasti c 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

CBR Unsoaked (0 Hrs.)

CBR soaked (24 Hrs.)


CBR soaked (72Hrs.)

CBR with 4 day Soaking

18.57

9.66

7.14

6.05

5.02

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

Fig. No. 2

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

Fig. No. 4

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

Fig. No. 6

CBR with 96 Hrs. Soaking Sample No. 1

VARIATION OF CBR WITH TIME OF SOAKING SAMPLE NO. 1




CBR soaked (72Hrs.)

CBR with 4 day Soaking (96 Hrs.)

18.57

9.66

7.14

6.05

5.02

20.00 18.00 16.00 14.00 )

12.00

% n i

10.00

R B C 8.00 6.00 4.00 2.00 0.00

0.0

20.0

40.0

60.0 Time in Hour's

80.0

100.0

120.0



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

Atterberg's Limit

Liquid Limit (LL) %

Plastic Limit (PL) %


34.50

20.53

13.97

Free Swell Index


29.25

1.9

OMC%




CBR soaked (72Hrs.)


12

25.25

13.37

10.40

7.35

6.19

Observation Reports of Sample No. 2 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. 7 (Grain Size Analysis of sample no. 2

Fig. No. 9 LL & PL T

Result of

le no. 2

Fig. No. 10

Fig. No. 11 (CBR Test Result (24 Hrs.) of sample no. 2




Fig. No. 14 f




CBR soaked (72Hrs.)


25.25

13.37

10.40

7.35

6.19


30.00

25.00

20.00 )

% n i

15.00

R B C

10.00

5.00

0.00 0.0

20.0

40.0

60.0

80.0

100.0

Time in Hour's

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

120.0



Table No. 8 (Analysis of sample no. 3) Atterberg's Limit Liquid Limit (LL) %



33.26

20.53

12.73

Free Swell Index


16.3

1.87

OMC%




CBR soaked (72Hrs.)


9

21.54

12.63

11.88

10.40

8.37

Observation Reports of Sample No. 3 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. 9 (Grain size analysis of sample no. 3)

Fig. No. 16

Fig. No. 17

Fig. No. 19 l f

l

Fig. No. 20




CBR soaked (72Hrs.)


21.54

12.63

11.88

10.40

8.37


30.00

25.00

20.00 )

% n i

15.00

R B C

10.00

5.00

0.00 0.0

20.0

40.0

60.0

80.0

100.0

Time in Hour's


120.0



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

Atterberg's Limit

Liquid Limit (LL) %


Plasticit y Index (PI) %

31.53

20.53

11.00

Free Swell Index

Mas Dry Densit y gm/cc

19.3

1.93

OMC %

CBR Unsoake d (0 Hrs.)



CBR soaked (72Hrs. )

CBR with 4 day Soakin g

10

17.83

9.66

8.91

7.43

5.31

Observation Reports of Sample No. 4 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. 11 (Grain Size Analysis of sample No 4)

Fig. No. 24

Fi . No 25

Fig. No. 26

Fig. No. 27 (CBR Test Result (72Hrs.) of sample no. 4


VARIATION OF CBR WITH TIME OF SOAKING SAMPLE NO.4




CBR soaked (72Hrs.)


17.83

9.66

8.91

7.43

5.31

20.00 18.00 16.00 14.00 )

%12.00 n i 10.00

R B 8.00 C 6.00 4.00 2.00 0.00 0.0

20.0

40.0

60.0

80.0

100.0

Time in Hour's


120.0

CHAPTER - 5 CONCLUSIONS & 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 understand the influence of soaking on CBR value 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)

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

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

REFERENCES 

Arora K.R. “A Text book of Soil Mechanics”



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



Berry D.S. K.B. and Goetz Woods, W.H. Highway Engineering Hand Book, McGraw Hill Book Co. Inc. India.



Khanna S.K. and C.E.G. Justo, Nem Chand & Bros; Roorkee Highway engineering.



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



Punmia B.C., Ashok Kumar Jain & Arun Kumar Jain “A Text Book of Soil Mechanics & Foundations”.



Sahoo Biswajeet & Nayak Devadatta, (2009) "A Study of Subgrade Strength Related to moisture"



Singhal, R.P. (1967). Soil Mechanics and Foundation Engineering, Singhal Publications, India.



Terzaghi, K. (1943). Theoretical soil Mechanics, Chapman and Hall, London and John Wiley & Sons.



Terzaghi, K. and Peck, R.B. (1967). Soil Mechanics in engineering practice, Hohn Wiley & Sons.



Yoder, E.J., Principles of pavement design, John Wiley and Sons, India.



“Guidelines for the Design of Flexible Pavements for low volume of Rural road” IRC- SP-72,



IS 2720 Part-5 “Method of test for Soil-Determination of Liquid limit and Plastic limit”



IS 2720 Part –8 “Method of test for Soil-Determination of Water Content, Dry density relation using a heavy Compaction”

 IS 2720 Part-16 “Methods of test for Soil-Laboratory determination of CBR ”Partha Chakroborty &

Animesh Das “Principles of Transportation Engineering” Ministry of Road Transport and Highways Report of the Specifications for Road and Bridge Work in India. 

IRC-SP 72-2007, "Guidelines for the Design of Flexible Pavements for Low Volume Rural Roads" IRC, New Delhi.



Indian Roads Congress, Guidelines for the design of flexible pavements (second revision), IRC : 37-2001.

Thesis IN M.TECH

Recommend Documents