SOIL MECHANICS : Particle Size Distribution Of Soil

AIM

This test is done to determine the particle size distribution of soil as per

IS: 2720 (Part 4) – 1985.

APPARATUS

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

PROCEDURE

i) The dried sample is taken in a tray, soaked in water and mixed with either 2g of sodium hexa-meta- phosphate or 1g of sodium hydroxide and 1g of sodium carbonate per liter of water, which is added as a discursive agent. The soaking of soil is continued for 10 to 12hrs.

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

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

iv) This sample of about 200g is washed through 75µm IS Sieve with half liter 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 24 hrs. The dried soil sample is sieved through 2 mm, 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 analyze soil particle size.

OBSERVATION

RESULTS

The results are plotted on a semi-log graph with particle size as abscissa .