Grain size analysis (GSA)of soil IS 2720-Part 4

To determine the grain size analysis of soil (Wet analysis)

TEST STANDARD: IS 2720-Part 4:1985

APPARATUS:

1. Weighing balance of accuracy 0.1gm
2. IS Sieves of 100mm, 75mm, 19mm, 4.75mm, 2mm, 425microns and 75microns
3. Sieve brush
4. Hot air oven, GI tray, Sodium hydroxide and sodium carbonate.

PROCEDURE FOR GRAIN SIZE ANALYSIS

The soil sample received from the field shall be dried in the oven at 105 °Cto 110 °C, the clods may be broken with a rubber pestle without reducing the size of the individual grains to hasten drying.

The organic matter like tree roots and pieces of bark shall be removed from the sample, shells if any, shall be separated and the percentage of their presence shall be noted.

1. The oven dried sample shall be taken by quartering method to have a minimum weight of 60kg for 75mm, 25kg for 37.5mm, 13kg for 25mm, 6.5kg for 19mm, 3.5kg for 12.5mm, 1.5kg for 10mm, 0.75kg for 6.5mm and 0.4kg for 4.75mm size of material.
2. Mixture of 1.0 gms of sodium hydroxide and 1 gms of sodium carbonate diluted to one litre water shall then be added into the soil. Mix should be thoroughly stirred and left for soaking for a period of period of 2 hours.
3. Wash the sample under water by allowing the washed water to go through the lowest size of sieve, i.e., 75microns.
4. Wash the sample till the water passing the sieve is substantially clean, collect all the material retained on 75microns, drain out the excess water and keep it oven for 24hours at 105 °C to 110 °C. Allow the sample to cool, and perform dry sieving with the largest size of sieve first and the next sizes consecutively.
5. Ensure that the sieving is complete, and the amount of material retained on each sieve shall be weighed and noted.

The cumulative mass of the soil fraction shall be then calculated, and percentage of passing on each sieve shall then be reported for Grain size analysis (GSA)

1. The material passing 100mm sieve and retains on 75mm sieve is called ‘Cobble’.
2. The material passing 75mm sieve and retains on 4.75mm sieve is called ‘Gravel’.
3. The material passing 4.75mm sieve and retains on 75microns is called ‘Sand’.
4. The material passing 75microns sieve is called ‘Silt and clay’

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