The following test results were obtained for a fine-grained soil:
       W_L= 48% ; W_P = 26%
      Clay content = 55%
      Silt content = 35%
      Sand content = 10%
      In situ moisture content = 39% = w

Classify the soil, and determine its activity and liquidity index

Solution:

Plasticity index, I_P = W_L– W_P = 48 – 26 = 22%

Liquid limit lies between 35% and 50%.

According to the Plasticity Chart, the soil is classified as CI, i.e. clay of intermediate plasticity.

Liquidity index , = = 0.59

The clay is of normal activity and is of soft consistency.