Question

A fully saturated soil has water content of 20% and specific gravity 2.5, then its porosity is ..........

• A. 66.66%
• B. 33.33%
• C. 25%
• D. 50%

Hint:

Use: $e = \dfrac{w \cdot G}{S}$ and $n = \dfrac{e}{1+e}$
This approach is crucial for porosity calculations in saturated soils.

Answer 1

The Correct Option is B

Given:
Water content, $w = 20% = 0.2$
Specific gravity of soil solids, $G = 2.5$
Fully saturated soil $⇒ S = 1$
We use the relation for void ratio in saturated soil:
$e = \dfrac{w \cdot G}{S} = \dfrac{0.2 \cdot 2.5}{1} = 0.5$
Now, porosity $n$ is given by:
$n = \dfrac{e}{1 + e} = \dfrac{0.5}{1 + 0.5} = \dfrac{0.5}{1.5} = 0.3333$
Therefore, porosity $n = 33.33%$