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Determine Free Swell Index Of Soil

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

strong>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 = [Vd – Vk] / Vk x 100%
where,
Vd = volume of soil specimen read from the graduated cylinder containing distilled water.
Vk = volume of soil specimen read from the graduated cylinder containing kerosene.

Free Swell

Index

Degree of

expansiveness

LL

PL

SL

<20

Low

0.50

0-35%

>17%

20-35

Moderate

40-60%

25-50%

8-18%

35-50

High

50-75%

35-65%

6-12%

>50

Very high

>60%

>45%

<10%

We are thankful to Er Jithesh for submitting the table to us

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Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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29 comments on "Determine Free Swell Index Of Soil"

sameer singh says:

what value should be suitable for using soil at different places such as for subgrade,for foundation…according to IS codes.ans what is significance of this test

Er A K Samal says:

Very useful

Lee Jong-Min says:

I’ve seen the material given. Thankyou so much.
However, I have a question and leave a comment.
What is the ‘LL, PL, SL’ on the right side of the table?
Please reply me. Thanks~

Jagdish Chand Sharma says:

Sir
Please tell me those situations when soil volume increase in kerosin and remain constant in water.Is it possible ?
Let me know about in detail.
Thanks and regards.

J.C.Sharma

Abhimanyu Padhi says:

Sir, Good day. Gods grace I got this link. I have a bore piling project in which the properties of bentonite is given ” The differential free swell shall be more than 540 percent”. In your post above it is felt that the this value is very high. Will this high value will come for bentonite? Please advice.

Naman kumar says:

SL full form

Ravi kumar says:

Why kerosene oil is use in this test and which other oil we can used instead of kerosene oil

Arif says:

What to use in place of kerosene oil, if it is not available.

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