Question

Consider the following properties for clays X and Y:


Which of the clays, X or Y, experiences larger settlement under identical loads, is more plastic and is softer in consistency?

• A. X, Y, and X
• B. Y, X and X
• C. Y, X and Y
• D. X, X and Y

Answer 1

The correct option is C Y, X and Y

(c)
Plasticity Index$\left(I_P\right)$ is the numerical difference between liquid limit and plastic limit. The soil with higher value of $I_P$ will be more plastic.

${\left(I_P\right)}_X=42-20=22$

${\left(I_P\right)}_Y=56-34=22$

But if plasticy index is same for both soils, then the soil with larger difference in liquid limit and natural water content is more plastic.
Consistency Index,

$I_C=\frac{Liquidlimit-Naturalwatercontent}{I_P}$

$\therefore (I_C{)}_X=\frac{42-30}{22}=0.545$

${\left(I_C\right)}_Y=\frac{56-20}{22}=0.273$

Soil which has low value of consistency index is softer. Thus the softer soil will undergo large settlements under identical loads.