All laboratory tests were performed by qualified and experienced personnel, familiar with and having access to equipment and facilities for the accurate determination of data necessary. Laboratory tests were carried out in accordance with the procedures described in the relevant BIS codes of practiced.
Selected Disturbed Soil Samples collected from boreholes and trial pits were tested for the following tests: All tests shall be carried out as per relevant parts of IS 2720.
Natural Moisture content of soil is the percentage of water present in the soil with respect to the weight of solids. For this test quantity of sample was taken as per IS: 2720 (Part -2) and weighed accurately to 0.01 gms along with
the can (W1). Then the sample was oven dried at 105°C for 24 hrs. Then the oven dried weight of the sample along with the can was weighed.
accurately to 0.01 gms (W2). The empty weight of the can was also measured. (W3). Then the NMC was calculated as – NMC (%) = Wt of Water / Wt. of Solids * 100
The test was conducted as per IS 2720 – Part 3. Specific Gravity of soils shall be determined using Pycnometer. The weight of the bottle and cap was measured accurately (W1). Small quantity of oven dried sample was transferred to density
bottle and weighed together (W2). Sufficient air-free distilled water was added to the bottle so that the soil in the bottle was just covered. The entrapped air was removed by either placing in desiccator or by heating the pycnometer.
Then the density bottle or pycnometer was filled completely with water and weighed accurately (W3). The bottle was then be cleaned and filled entirely with water only. The weight was measured accurately (W4). Then the specific
gravity was calculated as –
G = W2 - W1/ (W4 - W1) - (W3-W2)
The test was conducted in two parts – Sieve analysis for particles greater than 75 µ size and hydrometer analysis for particles less than 75 µ size.
The quantity of sample for testing was as per IS: 2720 (Part – 4). For sieve analysis
oven dried sample was taken after treating by dispersion agent and passing from 4.75 mm sieve. The sample was sieved through various sieve arranged in sequence as – 4.75 mm , 2.36 mm, 1.18 mm. 900 µ, 425 µ, 300 µ, 150 µ and 75
µ.
For Hydrometer analysis sample size was as per IS: 2720 (Part 1 & 4) to be taken oven dried passing through 75 µ sieve. The suspension of 1000 ml was prepared after treating the sample with H₂O₂, HCl and dispersing agent.
Then the reading was taken at the specified time intervals using hydrometer.
The graph was plotted for diameter (or particle size) versus percentage finer. The various percentages were calculated as follows –
Gravels Particles
greater than 4.75 mm
Sand Particles between 4.75 mm and 0.075 mm (75 µ)
Silt Particles between 0.075 mm (75 µ) and 0.002 mm (2 µ)
Clay Particles smaller than 0.002 mm (2 µ)
This is the test to determine the state of the soil – solid state; plastic state or liquid state.
The two properties - liquid limit and plastic can determine the state of the solids.
The sample for the testing was as per IS:
2720 (Part – 1, 5 & 6). The paste was prepared and placed in the liquid limit apparatus and a groove was made using grooving tool. Blows were applied the number of blows were measured at which two parts of the paste were come in
contact. The test was repeated for 3 to 4 different water content and by plotting the graph the water content required for the 25 blows was determined. This water content required for 25 blows was termed as “Liquid limit”.
For determination Plastic Limit about 25 gms of oven dried sample (passing 400 µ sieve) was taken and thoroughly mixed with water. The soil was rolled between hand and glass plate so as to form a thread of 3 mm diameter. The soil
was kneaded and rolled again so that the moisture was gradually reduced. The process was repeated until the soil thread of 3 mm diameter was just crumbled. This moisture content was recorded as “Plastic Limit”.
For determination
of shrinkage limit about 30 gms of oven dried samples was taken. Water was thoroughly mixed to make it enough pasty and filled in shrinkage dish without entrapping air bubbles. The sample was oven dried. The volume of oven dried
sample and shrinkage dish was determined using mercury displacement method and the shrinkage limit was evaluated.
The selected samples were tested for free swell index test as per IS: 2720 (Part – 40). Two specimens of measured quantity of oven dry soil (5 gms or 10 gms) were taken and poured in each oftwo graduated cylinders. One cylinder was filled with kerosene and one was filled with distilled water upto 100 ml mark. After removal entrapped air allow the soil to settle. After 24 hrs the final volume of soils in each cylinder was measured as Vw and Vk – volume of soil in cylinder filled with water and volume of soil in cylinder filled with kerosene respectively. Then the free swell index FSI was determined as – FSI = Vw - Vk/ Vk x100 In addition to these tests the UDS collected from boreholes as well from Trial Pits were tested for the following tests.
Bulk density is the ratio of mass of moist soil to the volume of soil sample. Bulk density was evaluated from UDS. A representative sample was cut from the extruded UDS and dimensions of sample were measured. Weight of the sample was measured and density was determined as weight / volume.
Selected rock cores were tested in Laboratory for the following tests.
Specific Gravity of the rock specimen was determined using Pycnometer.
The test was carried out as per IS 13030. Water absorption was expressed as the percentage of water content with respect to the dry weight of the sample. For this small piece of rock sample was taken and weighed accurately to 0.01
gms (W1). Then the sample was oven dried at 105⁰C for 24 hrs. Then the oven dried weight of the sample was weighed accurately to 0.01 gms (W2). Then the water absorption calculated as –
Water absorption (%) = Wt of Water /
Wt. of Specimen * 100
The tests shall be carried out as per IS 9143. Test specimen was prepared from the cores obtained from field having l/d ratio preferably 2. If ratio was less than this suitable correction is applied. The specimen was fixed between the horizontal platens. Load was applied to the specimen at a constant stress rate such that failure has taken place in about 5 to 15 minutes of loading.
The tests was carried out as per IS 9143.Test was conducted on circular cylindrical sample having l/d ratio of 2 to 3. Load was applied continuously and without shock to produce an approximately constant rate of load or deformation such that failure will occur within 5 to 15 minutes of initiation of loading if carried to failure. Load and the axial and diametrical or circumferential strains were measured frequently at evenly spaced load intervals during the test.
The selected samples of soil and water were tested for pH, sulphates and chlorides.
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