Question

A specimen of clayey silt contains 70% silt size particles. Its liquid limit = 40 and plastic limit = 20. In liquid limit test, at moisture content of 30% required number of blows was 50. Its plasticity index, activity and consistency index will respectively be

• A. 20, ,0.67 and 0.5
• B. 20, 1.5 and 2.0
• C. 30, 1.5 and 0.72
• D. 20, 0.286 and 0.38

Answer 1

The correct option is A 20, ,0.67 and 0.5

(a)
$PlasticityIndex,I_P=W_L-W_P$
= 40 - 20 = 20

Activity of clay,

$A_C=\frac{Plasticityindex}{Percentfinerthan2\mu }$

$=\frac{Plasticityindex}{Percentofclaysizeparticlesinthesoil}$

$=\frac{20}{100-70}=0.67$

Consistency Index,

$=\frac{W_L-W_N}{I_P}=\frac{40-30}{20}$

= 0.50