A soil has liquid limit of 25% and flow index of 12.5%. If the plastic limit is 50%, determine the plasticity index & toughness index. If water content of the soil in its natural condition in the field is 20%, find the liquidity index & relative consistency.

Given Data:

$I_l=25%$

$I_f=12.5%$

$W_p=25%$

$\text{Natural water content W=20%}$

$\text{P.I or }I_p=W_l-W_p$

$=25-15$

$=10%$

$I_t=\frac{I_p}{I_f}=\frac{10}{12.5}=0.8$(80%)

$I_l=\frac{W-W_p}{I_p}\times 100$

$=\frac{0.20-0.15}{0.10}\times 100$

$\text{=50%}$

$I_c=\frac{W_l-W}{I_p}\times 100$

$=\frac{0.25-0.20}{0.10}\times 100$

$\text{=50%}$