To determine the free swell index of soil as per IS: 2720 (Part XL) - 1977. Free swell or differential free swell, also termed as free swell index, is the increase in volume of soil without any external constraint when subjected to submergence in water. The apparatus used :

i) IS Sieve of size 425µm
ii) Oven
iii) Balance, with an accuracy of 0.01g
iv) Graduated glass cylinder- 2 nos., each of 100ml capacity

Procedure to determine Free Swell Index Of Soil

i) Take two specimens of 10g each of pulverised soil passing through 425µm IS Sieve and oven-dry.

ii) Pour each soil specimen into a graduated glass cylinder of 100ml capacity.

iii) Pour distilled water in one and kerosene oil in the other cylinder upto 100ml mark.

iv) Remove entrapped air by gently shaking or stirring with a glass rod.

v) Allow the suspension to attain the state of equilibrium (for not less than 24hours).

vi) Final volume of soil in each of the cylinder should be read out.

REPORTING OF RESULTS

Free swell index = [V_d - V_k] / V_k x 100%

where,

V_d = volume of soil specimen read from the graduated cylinder containing distilled water.

V_k = volume of soil specimen read from the graduated cylinder containing kerosene.

This test is done to determine the plastic limit of soil as per IS: 2720 (Part 5) - 1985.The plastic limit of fine-grained soil is the water content of the soil below which it ceases to be plastic. It begins to crumble when rolled into threads of 3mm dia. The apparatus used:

i) Porcelain evaporating dish about 120mm dia.
ii) Spatula
iii) Container to determine moisture content
iv) Balance, with an accuracy of 0.01g
v) Oven
vi) Ground glass plate - 20cm x 15cm
vii) Rod - 3mm dia. and about 10cm long

PREPARATION OF SAMPLE
Take out 30g of air-dried soil from a thoroughly mixed sample of the soil passing through 425µm IS Sieve. Mix the soil with distilled water in an evaporating dish and leave the soil mass for naturing. This period may be upto 24hrs.

Procedure to determine The Plastic Limit Of Soil
i) Take about 8g of the soil and roll it with fingers on a glass plate. The rate of rolling should be between 80 to 90 strokes per minute to form a 3mm dia.

ii) If the dia. of the threads can be reduced to less than 3mm, without any cracks appearing, it means that the water content is more than its plastic limit. Knead the soil to reduce the water content and roll it into a thread again.

iii) Repeat the process of alternate rolling and kneading until the thread crumbles.

iv) Collect and keep the pieces of crumbled soil thread in the container used to determine the moisture content.

v) Repeat the process at least twice more with fresh samples of plastic soil each time.

REPORTING OF RESULTS
The plastic limit should be determined for at least three portions of the soil passing through 425µm IS Sieve. The average water content to the nearest whole number should be reported.

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. It’s flow closes the groove in just 25 blows in Casagrande’s liquid limit device. The apparatus used :-
i) Casagrande’s liquid limit device
ii) Grooving tools of both standard and ASTM types
iii) Oven
iv) Evaporating dish
v) Spatula
vi) IS Sieve of size 425µm
vii) Weighing balance, with 0.01g accuracy
viii) Wash bottle
ix) Air-tight and non-corrodible container for determination of moisture content

PREPARATION OF SAMPLE
i) Air-dry the soil sample and break the clods. Remove the organic matter like tree roots, pieces of bark, etc.
ii) About 100g of the specimen passing through 425µm IS Sieve is mixed thoroughly with distilled water in the evaporating dish and left for 24hrs. for soaking.

Procedure to Determine The Liquid Limit Of Soil
i) Place a portion of the paste in the cup of the liquid limit device.

ii) Level the mix so as to have a maximum depth of 1cm.

iii) Draw the grooving tool through the sample along the symmetrical axis of the cup, holding the tool perpendicular to the cup.

iv) For normal fine grained soil: The Casagrande’s tool is used to cut a groove 2mm wide at the bottom, 11mm wide at the top and 8mm deep.

v) For sandy soil: The ASTM tool is used to cut a groove 2mm wide at the bottom, 13.6mm wide at the top and 10mm deep.

vi) After the soil pat has been cut by a proper grooving tool, the handle is rotated at the rate of about 2 revolutions per second and the no. of blows counted, till the two parts of the soil sample come into contact for about 10mm length.

vii) Take about 10g of soil near the closed groove and determine its water content

viii) The soil of the cup is transferred to the dish containing the soil paste and mixed thoroughly after adding a little more water. Repeat the test.

ix) By altering the water content of the soil and repeating the foregoing operations, obtain at least 5 readings in the range of 15 to 35 blows. Don’t mix dry soil to change its consistency.

x) Liquid limit is determined by plotting a ‘flow curve’ on a semi-log graph, with no. of blows as abscissa (log scale) and the water content as ordinate and drawing the best straight line through the plotted points.

REPORTING OF RESULTS
Report the water content corresponding to 25 blows, read from the ‘flow curve’ as the liquid limit.
A sample ‘flow curve’ is given as

This test is done to determine the particle size distribution of soil as per IS: 2720 (Part 4) - 1985. The appratus required to do this test :-
i) A set of fine IS Sieves of sizes - 2mm, 600µm, 425µm, 212µm and 75µm
ii) A set of coarse IS Sieves of sizes - 20mm, 10mm and 4.75mm
iii) Weighing balance, with an accuracy of 0.1% of the weight of sample
iv) Oven
v) Mechanical shaker
vi) Mortar with rubber pestle
vii) Brushes
viii) Trays

PREPARATION OF SAMPLE
i) Soil sample, as received from the field, should be dried in air or in the sun. In wet weather, the drying apparatus may be used in which case the temperature of the sample should not exceed 60^oC. The clod may be broken with wooden mallet to hasten drying. Tree roots and pieces of bark should be removed from the sample.

ii) The big clods may be broken with the help of wooden mallet. Care should be taken not to break the individual soil particles.

iii) A representative soil sample of required quantity as given below is taken and dried in the oven at 105 to 120^oC.

Procedure to determine Particle Size Distribution Of Soil
i) The dried sample is taken in a tray, soaked in water and mixed with either 2g of sodium hexametaphosphate or 1g of sodium hydroxide and 1g of sodium carbonate per litre of water, which is added as a dispersive agent. The soaking of soil is continued for 10 to 12hrs.

ii) The sample is washed through 4.75mm IS Sieve with water till substantially clean water comes out. Retained sample on 4.75mm IS Sieve should be oven-dried for 24hrs. This dried sample is sieved through 20mm and 10mm IS Sieves.

iii) The portion passing through 4.75mm IS Sieve should be oven-dried for 24hrs. This oven-dried material is riffled and about 200g taken.

iv) This sample of about 200g is washed through 75µm IS Sieve with half litre distilled water, till substantially clear water comes out.

v) The material retained on 75µm IS Sieve is collected and dried in oven at a temperature of 105 to 120^oC for 24hrs. The dried soil sample is sieved through 2mm, 600µm, 425µm
and 212µm IS Sieves. Soil retained on each sieve is weighed.

vi) If the soil passing 75µm is 10% or more, hydrometer method is used to analyse soil particle size.

HYDROMETER ANALYSIS
i) Particles passed through 75µm IS Sieve along with water are collected and put into a 1000ml jar for hydrometer analysis. More water, if required, is added to make the soil water suspension just 1000ml. The suspension in the jar is vigorously shaken horizontally by keeping the jar in-between the palms of the two hands. The jar is put on the table.

ii) A graduated hydrometer is carefully inserted into the suspension with minimum disturbance.

iii) At different time intervals, the density of the suspension at the centre of gravity of the hydrometer is noted by seeing the depth of sinking of the stem. The temperature of the suspension is noted for each recording of the hydrometer reading.

iv) Hydrometer readings are taken at a time interval of 0.5 minute, 1.0 minute, 2.0 minutes, 4.0 minutes, 15.0 minutes, 45.0 minutes, 90.0 minutes, 3hrs., 6hrs., 24hrs. and 48hrs.

v) By using the nomogram given in IS: 2720 (Part 4) - 1985, the diameter of the particles for different hydrometer readings is found out.

REPORTING OF RESULTS
After completing mechanical analysis and hydrometer analysis, the results are plotted on a semi-log graph with particle size as abscissa (log scale) and the percentage smaller than the specified diameter as ordinate

This test is done to determine the water content in soil by calcium carbide method as per IS: 2720 (Part II) - 1973. It is a method for rapid determination of water content from the gas pressure developed by the reaction of calcium carbide with the free water of the soil. From the calibrated scale of the pressure gauge the percentage of water on total mass of wet soil is obtained and the same is converted to water content on dry mass of soil.

Apparatus required :-
i) Metallic pressure vessel, with a clamp for sealing the cup, alongwith a gauge calibrated in percentage water content
ii) Counterpoised balance, for weighing the sample
iii) Scoop, for measuring the absorbent (Calcium Carbide)
iv) Steel balls - 3 steel balls of about 12.5mm dia. and 1 steel ball of 25mm dia.
v) One bottle of the absorbent (Calcium Carbide)

PREPARATION OF SAMPLE
Sand - No special preparation. Coarse powders may be ground and pulverized. Cohesive and plastic soil - Soil is tested with addition of steel ball in the pressure vessels. The test requires about 6g of sample.

Procedure to determine Water Content In Soil By Calcium Carbide Method
i) Set up the balance, place the sample in the pan till the mark on the balance arm matches with the index mark.

ii) Check that the cup and the body are clean.

iii) Hold the body horizontally and gently deposit the levelled, scoop-full of the absorbent (Calcium Carbide) inside the chamber.

iv) Transfer the weighed soil from the pan to the cup.

v) Hold cup and chamber horizontally, bringing them together without disturbing the sample and the absorbent.

vi) Clamp the cup tightly into place. If the sample is bulky, reverse the above placement, that is, put the sample in the chamber and the absorbent in the cup.

vii) In case of clayey soils, place all the 4 steel balls (3 smaller and 1 bigger) in the body along with the absorbent.

viii) Shake the unit up and down vigorously in this position for about 15 seconds.

ix) Hold the unit horizontally, rotating it for 10 seconds, so that the balls roll around the inner circumference of the body.

x) Rest for 20 seconds.

xi) Repeat the above cycle until the pressure gauge reading is constant and note the reading. Usually it takes 4 to 8 minutes to achieve constant reading. This is the water content (m) obtained on wet mass basis.

xii) Finally, release the pressure slowly by opening the clamp screw and taking the cup out, empty the contents and clean the instrument with a brush.

REPORTING OF RESULTS
The water content on dry mass basis,
w=m/[100-m] * 100%