A soil has bulk density of 20.1 kN/m³ and water content 15%. What is the water content if the soil partially dries to a density of 19.4 kN/m³ and the void ratio remains unchanged ?

Question

Question

This question was previously asked in

ESE Civil 2021 Official Paper

Answer 1

Explanation:

Given,

Case - I: Bulk density = 20.1 kN/m³, water content = 15%

Case II: Dry Density = 19.4 kN/m³⇒ water content = ??

No change in void ratio.

As, dry unit weight (γd) = γ/(1 + w)

\(\begin{array}{l} {γ_d} = \frac{γ}{{1 + w}} = \frac{{20.1}}{{1 + 0.15}} = 17.478\; kN/{m^3}\\ {γ_d} = \frac{{{γ_w}.G}}{{1 + e}} \end{array}\)

If void ratio 'e' remains unchanged during drying, \(γ_d\) also remains unchanged.

\(\begin{array}{l} {\gamma_d} = \frac{\gamma}{{1 + w}}\\ 17.478 = \frac{{19.4}}{{1 + w}} \end{array}\)

w = 10.99 %

Hence, The most appropriate answer is option 1.