FREE SWELL INDEX

Updated: May 1, 2020

AIM

To determine the free swell index of soil as per IS: 2720

(Part XL) - 1977.

PRINCIPLE

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.

APPARATUS

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

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 24hrs.).

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

out.

REPORTING OF RESULTS



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