Question

If natural water content (w) of a soil sample is equal to its plastic limit (\(w_p\)), then the consistency index of the soil will be:

• A. 0
• B. 1
• C. -0.5
• D. 1.5

Hint:

If $w = w_p$, consistency index ($I_c$) is always $1$. This is a critical point in classifying soil plasticity.

Answer 1

The Correct Option is B

The consistency index ($I_c$) is defined as:
\[I_c = \frac{w_l - w}{w_l - w_p}\]
where:
$w_l$: Liquid limit.
$w$: Natural water content.
$w_p$: Plastic limit.
When $w = w_p$, substitute into the formula:
\[I_c = \frac{w_l - w_p}{w_l - w_p} = 1\]