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TESTING METHODOLOGY 4.1 General For the present study, the samples had been collected nearby the Bemina Chowk area adjacent to the N.H. Bye-Pass from a test pit at a depth of 1m from the ground surface level. The test pit had already been dug by the agency that wanted the tests to be done by a certified agency. Both disturbed and undisturbed samples have been taken from the site. 4.2 Sampling Details •

Undisturbed Samples

Core cutters, CBR moulds have been used. Three samples of core cutters were taken and the CBR moulds have been procured for the determination of bulk density, moisture content, CBR value and the undisturbed unconfined compression strength. Care has been exercised while ramming the samplers into the ground. The dynamic pushes were avoided as far as possible to preserve the natural conditions. The samples obtained were carefully placed in polythene bags and labeled properly. •

Disturbed Samples

About a gunny bag full of loose soil has been taken from the location. Although the natural structure of the soil gets disturbed during sampling yet these samples represents the composition and mineral content of the soil.

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4.3 Testing Methodology The study is divided into two parts: Part 1 Characterization of the soil obtained from the site. Part 2 Study of the behaviour of sand on the CBR behavior of fine grained soils. Part 1 Characterization of the soil obtained from the site. For the characterization of the soil obtained from the site the general test are conducted and the soil so obtained is characterized by an evaluation of its physical properties and engineering properties

4.3.1 Physical Properties The physical properties of the soil so procured are obtained by the evaluation of a) Field capacity and moisture content. b) Grain size distribution c) Specific gravity. d) Atterberg’s limits. 4.3.2 Geotechnical properties The geotechnical properties are used to determine a) Compaction characteristics b) Strength characteristics. 4.3.3 Testing program The program includes evaluation of physical and geotechnical properties.

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TESTING METHODOLOGY

4.4 Physical properties Following are the tests conducted on the procured soil to determine its physical properties

4.4.1 Field Density and Moisture Content The usual methods of measuring density of the in-situ are core cutter and sand replacement methods. The field density has been determined by the commonly employed core cutter techniques. (IS: 2720, Part 29, 1975). The water content has been determined by oven drying method (IS: 2720, Part 2, 1973). A typical data sheet for the determination of the same has been presented below

Table 4.1 Data Sheet for Bulk Density

SAMPLE NO.

WEIGHT OF CORE CUTTER (g)

WEIGHT OF CORE CUTTER+SOIL (g)

WEIGHT OF SOIL (g)

BULK DENSITY (g/cm3)

1 2 3

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Table 4.2 Data Sheet for Moisture Content WEIGHT OF WEIGHT OF WEIGHT WEIGHT OF SAMPLE EMPTY CONTAINER OF CONTAINER+WET NO. CONTAINER + DRY SOIL WATER SOIL (g) (g) (g) (g)

MOISTURE CONTENT (%)

1 2 3

4.4.2 Specific Gravity The specific gravity of the soil solids is determined by density bottle method for fine grained soils (laboratory method) and gas jar method for all soils (field method). The specific gravity has been determined by density bottle method (IS : 2720, Part 3/Sec 1,2, 1980). A typical data sheet for the determination of the same has been presented below.

Specific Gravity determination MASS OF EMPTY BOTTLE (M1) = MASS OF BOTTLE + MOIST SOIL (M2) = MASS OF BOTTLE + MOIST SOIL + WATER (M3) = MASS OF BOTTLE + WATER (M4) = SPECIFIC GRAVITY=

M 2 − M1 = (M 4 − M 1 ) − (M 3 − M 2 )

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4.4.3 Grain Size Distribution Grain size is useful in determining the stability, resistance to shear, permeability, compressibility and compactibility of the soil. Grain size can be determined mechanically with sieves (direct) or indirectly by hydrometer or pipette methods. Sieving is not practical for silt or clay sized particles since they tend to clog the screen. When conducting grain size distribution on silt or clay sized particles, sedimentation in water (hydrometer or pipette methods) is preferred. Grain size distribution significantly impacts the weight bearing capacity of the soil. The grain size distribution has been carried out by sieve analysis for particles of size more than 75μ and by hydrometer analysis for particles of size less than 75μ. A typical data sheet for the determination of the same has been presented below.

Table 4.3 Typical data sheet for Particle size distribution (Sieve Analysis). SIEVE SIZE (mm)

MASS RETAINED (g)

%AGE MASS RETAINED

CUMULATIVE %AGE

4.75 2.36 1.18 0.50 0.30 0.15 0.075

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%AGE FINER

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TESTING METHODOLOGY

Table 4.4 Typical data sheet for Particle size distribution (Hydrometer Analysis) HYDRO TIME METER (t) READING (min.) (Ro)

Rh=(Ro-Rw) *1000

CORRECTED HYDRO TEMP METER (oC) READING R=Rh+C

He (cm)

D=M (mm)

He t

%AGE FINER

4.4.4 Atterberg’s Limits Consistency limits are extensively used in Geotechnical Engineering and these include liquid limit, plastic limit and shrinkage limit. •

Liquid limit

Liquid limit of a soil is the water content, expressed as a percentage of weight of oven-dried soil, at the boundary between liquid and plastic states of consistency of the soils. The liquid limit of the soil is determined by the flow curve. The water content corresponding to 25 blows is liquid limit. •

Plastic limit

The plastic limit of a soil is the water content, expressed as the percentage of ovendried soil, at the boundary between the semi-solids states of consistency of the soil. •

Plasticity index

Plasticity index is the difference of the liquid limit and the plastic limit. •

Shrinkage limit

Shrinkage limit is the maximum water content, expressed as the percentage of ovendried weight at which any further reduction in water content will not cause a decrease in the volume of soil.

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TESTING METHODOLOGY

Plasticity tests are conducted on the soil that is finer than 0.425 mm to determine the range of water content in which plasticity is exhibited. The type and amounts of clay particles present and water content, as well as the physicochemical interactions of clay particles, determine the plastic behaviour of the soil. The Atterberg’s limits, either individually or with other soil properties, can be correlated to other properties such as compactibilbity, compressibility, shear strength and permeability. The liquid limit has been determined by using mechanical liquid limit device (Casagrande’s apparatus). The plastic limit has been determined by the usual procedure of rolling 3mm diameter thread (of uniform diameter) and determining the water content at that stage by oven drying method. The shrinkage limit has been determined by mercury replacement method in conformation with IS: 2720, Part 6, 1972. Free swell Index has also been determined by using Kerosene oil. The data sheets corresponding to above mentioned consistency limits are as follows:

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TESTING METHODOLOGY

Table 4.5 Typical data sheet for Liquid Limit determination DETERMINATIO 1 N NO. NO. OF BLOWS WEIGHT OF CONTAINER (g) WEIGHT OF CONTAINER + WET SOIL (g) WEIGHT OF CONTAINER + DRY SOIL (g) WEIGHT OF WATER (g) WEIGHT OF DRY SOIL (g) WATER CONTENT (%)

2

3

4

Table 4.6 Typical data sheet for Plastic Limit determination DETERMINATION NO. 1 WEIGHT OF CONTAINER (g) WEIGHT OF CONTAINER + WET SOIL (g) WEIGHT OF CONTAINER + DRY SOIL (g) WEIGHT OF WATER (g) WEIGHT OF DRY SOIL (g) WATER CONTENT (%)

2

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TESTING METHODOLOGY

Table 4.7 Typical data Sheet for Shrinkage Limit determination DETERMINATION NO. WEIGHT OF SHRINKAGE DISH W1 (g) WEIGHT OF SHRINKAGE DISH + WET SOIL W2 (g) WEIGHT OF WET SOIL IN SHRINKAGE DISH W=W2-W1 (g) WEIGHT OF SHRINKAGE DISH + DRY SOIL W3 (g) WEIGHT OF DRY SOIL PAT WS =W3-W1 (g) VOLUME OF WET SOIL=VOLUME OF SHRINKAGE DISH V1 (cm3) VOLUME OF DRY SOIL PAT V2* (cm3) (W − WS ) − γ W (V1 −V2 ) SHRINKAGE LIMIT=

1

WS

Table 4.8 Typical data sheet for Swell Index determination

S.NO.

TIME ELAPSED

VOLUME OF SOIL IN KEROSENE (Vi) (cm3)

1 2 Thus, Free Swell Index (FSI) =

V f −Vi Vi

* 100 =

4.5 Geotechnical Properties DEPARTMENT OF CIVIL ENGINEERING

VOLUME OF SOIL IN WATER (Vf) (cm3)

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TESTING METHODOLOGY

4.5.1 Compaction Characteristics The density of soil is an important parameter since it controls its strength, compressibility and permeability. Compaction is the process of increasing the density of material by packing the particles close together with the reduction in volume of air. The compacted unit weight depends upon the amount and method of energy application and material properties such as grain size, gradation, particle shape, plasticity and the moisture content at compaction.

Compaction mechanically increases the amount of solids per unit volume of soil. It improves the engineering properties of the soil so that the required shear strength, structure, or void ratios are obtained, while decreasing the shrinkage, permeability and compressibility. The test aids in determining the percent compaction and water content necessary to obtain the desired engineering properties for construction. For any engineering application of soil, its strength characteristics are essential. In some special cases, as for checking the short-term stability of foundations and slopes where the rate of loading is fast but drainage is very slow, one of the most common shear tests is the unconfined compression test (UCT). UCT is the simplest and quickest test for determining the shear strength of cohesive soils. The results obtained from the unconfined compression tests serve as a direct quantitative measure if the consistency of cohesive soils, giving a clue to the danger of the rupture of embankment slopes or earth masses; give the stress-strain relationship under rapid failure conditions; provide basic information on strength properties, thus permitting us to estimate the possible bearing capacity of the soil in foundations and earthworks. The samples of the soil were the in-situ samples at natural bulk density and water content. The compaction characteristics viz. optimum moisture content (OMC) and maximum dry density (MDD) have been determined by Modified Proctor Test. The test results of the compaction test are presented in a plot of dry density versus water content. DEPARTMENT OF CIVIL ENGINEERING

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TESTING METHODOLOGY

The data sheet corresponding to the above mentioned is given below:

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TESTING METHODOLOGY

Modified Proctor Test Table 4.9 Data sheet for OMC and MDD determination DETERMINATION NO. 1 2 3 4 5 6 7 MASS OF MOULD (g) MASS OF MOULD+COMPACTED SOIL (g) MASS OF COMPACTED SOIL (g) WEIGHT OF EMPTY CONTAINER (g) WEIGHT OF CONTAINER+WET SOIL (g) WEIGHT OF CONTAINER+DRY SOIL (g) MOISTURE CONTENT (%) BULK DENSITY (g/cm3) DRY DENSITY (g/cm3) 4.5.2 Shear Strength Parameters The behaviour of the soil under load is a measure of its shear strength. Before a particular soil can be used for construction purposes, its shear strength must be determined (e.g. bearing capacity and stability of earthen slopes are directly related to shear strength). The value of cohesion ‘c’ has been determined by unconfined compression test (UCT). Following format has been used for recording the data

Table 4.10 Unconfined Compression Test record

S.NO.

STRAIN DIAL GAUGE

STRESS DIAL GAUGE

FORCE (kg)

CORRECTED STRAIN AREA (%) (A=A0/1-ε) (cm2)

1 2 3 4 5

DEPARTMENT OF CIVIL ENGINEERING

STRESS (kg/cm2)

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TESTING METHODOLOGY

4.5.3 California Bearing Ratio Test Of all the available methods of pavement design, the CBR method has been found to be the most reliable practical means of evaluating the strength of the subgrade or base course material (bearing capacity of the soil) and construction materials, and of estimating the required thickness of pavement to satisfy a given loading. The design of flexible pavement is generally guided by the criterion of CBR test, which is a measure of the load carrying capacity (resistance to direct penetration) of any soil or granular material, which is expressed as a percentage of the load carrying capacity of a standard crushed rock specimen (which is taken as 100% value) determined by a penetration test. Resistance to penetration of a rigid plunger is measured and the loads at penetrations of 2.5 mm and 5.0 mm are expressed as percentage of two standard loads (1370 kg and 2055 kg). The higher percentage is taken as the CBR value (usually at 2.5 mm penetration). The test may be carried out on intact samples taken from the subgrade or on sample compacted at 0.95 γdmax (preferably at modified proctor density) and corresponding water content on the dry side of optimum in the laboratory or the test may be performed in-situ. For highways, modified compaction hammer with a height of fall of 31 cm and weighing 4.89 kg is generally used and the sample compacted in five equal layers with 56 blows per layer. The data sheet corresponding to the above-mentioned test is presented below: Table 4.11

S.NO.

PENETRATION DIAL GAUGE LC=0.01 mm PENETRATION DGR (mm)

LOAD DIAL GAUGE READING LC-1 DIVN. =5.8 kg LOAD TOP BOTTOM AVERAGE (kg)

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TESTING METHODOLOGY

4.5.4 Direct Shear Test The shear strength of a soil mass is its property against sliding along internal planes within itself. In direct shear test, the sample is sheared along a horizontal plane. This indicates that the failure plane is horizontal. The normal stress on this plane is the external vertical load divided by the area of the soil sample. The test has been conducted on remoulded samples prepared at the OMC and MDD. The size of the samples so prepared was 6cm x 6cm and the thickness of the samples was 2.5cm. This test gives us the shearing strength parameter, which is very helpful in measuring the shear strength of a particular soil. Table 4.12

S.NO.

STRAIN DIAL GAUGE READING

SHEARING DISPLACEMENT ∂ (cm)

STRESS DIAL GAUGE READING

SHEAR STRESS (kg/cm2)

AXIAL STRAIN (%)

∂(cm ) ×100 L(cm )

Part 2 Study of the effect of sand on the CBR behavior of fine grained soils. The material which has been procured has been added with the sand procured from Ganderbal .The Sand has been added in the Soil in various percentages of 25%, 50%, 62.5%, 75% and 87.5% and the following test have been conducted on the mixture thereafter, 4.6 Compaction Characteristics of the soil mixture Modified Proctor Compaction of the soil mixture at all the percentages of sand has been carried out in order to determine OMC and MDD.

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TESTING METHODOLOGY

4.7 CBR Values of the soil mixture The CBR samples have been prepared at the OMC values of the respective soil mixtures and the CBR values have been determined for Soaked as well as unsoaked samples. The soaking of the soil mixture samples has been for the period of 4 days only. 4.8 Direct Shear Test Values Direct shear test has been performed on soil mixture prepared at various percentages of sand and the shear strength parameter “φ ” has been obtained from the plots.

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