To determine the free swell index of clayey soils

Object: To determine the free swell index of clayey soils

Apparatus:

• #40 (425micron) sieve.
  
• Graduated glass cylinders 100 ml capacity 2Nos.
  
• Glass rod for stirring.
  
• Balance of capacity 500grams and sensitivity 0.01 gram.
  

Need for free swell index:

There will be change in volume with the existence of the moisture. There will be increase in volume of the soil during the wet or rainy season and decrease in volume of the soil during the dry season. This may lead to the settlement of soil and leads to failure of foundation.

Swell index:

Swell index is also called as free swell index. When the volume of the soil increases without any application of external forces or water pressure, it is called as free swell. The index will measure the increase in volume with respect to the original volume.

Procedure:

1. Take two representative oven dried soil samples each of 10 grams passing through 425- micron sieve.
   
2. Pour each soil sample into each of the two glass graduated cylinders of 100ml capacity.
   
3. Fill one cylinder with kerosene and the other with the distilled water up to the 100ml mark.
   
4. Remove the entrapped air in the cylinder by gentle shaking and stirring with a glass rod.
   
5. Allow the samples to settle in both the cylinders.
   
6. Sufficient time, not less than 24 hours shall be allowed for soil sample to attain equilibrium state of volume without any further change in the volume of the soils.
   
7. Record the final volume of the soils in each of the cylinders.
   

Observations & Calculations:

𝐹𝑟𝑒𝑒 𝑆𝑤𝑒𝑙𝑙 𝐼𝑛𝑑𝑒𝑥 =

𝑣𝑑 − 𝑣𝑘

𝑣𝑘

𝑥100 ==

V_d=volume of the soil specimen read from the graduated cylinder containing distilled water V_k=volume of the soil specimen read from the graduated cylinder containing kerosene.

Results:

The free swell index of clayey soil is =%

Comments: