Free Swell Index of Soil : Objective, Apparatus, Procedure, Calculation & Observations

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Free Swell Index of soil is the raise in volume of a soil, without any external constraints, on submergence in water .

 

 

  1. Objective of Free Swell Index of Soil  

* To calculate the free swell index of expansive nature soil

 

 


 

 

  2. Apparatus  

The apparatus required to perform the free swell index is as follows:

a. Sieve – 425 Micron IS Sieve

b. Glass Graduated Cylinders – 100 ml capacity 2 Numbers (IS: 878 -1956)

c. Glass rod for stirring

d. Balance of capacity 500 grams and sensitivity 0.01 gram

 

 


 

 

  3. Procedure of Free Swell Index of Soil  

The procedure of free swell index of soil is as follows:

a. Bring two 10 gm soil specimens of oven-dry soil passing through 425 microns IS Sieve.

b. Spray each of the specimens into each of the two glass graduated cylinders of 100ml capacity.

c. Fill one cylinder with kerosene oil and the other with distilled water up to the 100ml mark. After removal of entrapped.

d. Air (by soft trembling or stirring with a glass rod), permits soils in both the cylinders to sink.

e. Permit enough time (not less than 24hrs) for the soil sample to get an equilibrium state of volume without any additional modification in the volume of the soils.

f. On completion of swelling, read out the final volume of soils in each of the cylinders.

 

Free swell index of soil

 

 


 

 

  4. Calculate the Free Swell Index Of Soil  

The level of the soil in the kerosene graduated cylinder shall be read as the original volume of the soil sample & kerosene being a non-polar liquid does not cause swelling of the soil.

The level of the soil in the distilled water cylinder shall be read as the free swell level.

The free swell index of the soil shall be calculated as follows:

Free swell index = (

Where,

Vd is the volume of soil specimen read from the graduated cylinder containing distilled water.

Vk is the 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%

 

 


 

 

  5. Observations in the Free Swell Index  

1. Volume of the soil specimen read from the graduated cylinder containing distilled water, Vd = ______ ml.

2. Volume of the soil specimen read from the graduated cylinder containing kerosene, Vk = ________ ml.

3. Free swell index = (Vd – Vk/ Vk) x 100 % = _________ x 100%

 

Reference : IS: 2720 (Part -40) – 1977

 

 

Results :

Free Swell Index = __________%

 

 


 

  6. References  

1. Content Filter & Authenticity Checking Team, Dream Civil International

(Our team checks every content & detail to maintain quality.)

 


 

 

Read Also: Calculate The Free Swell Index of Soil Index

 

 

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