Question

A retaining wall 3 m high, holds a backfill with $c=24kN/m^2$ and $\varphi ={30}^{\circ }$. In order to completely remove the possibility of tension cracks, the minimum surcharge that should be applied on the backfill is:

• A. $40kN/m^2$
• B. $23.09kN/m^2$
• C. $13.33kN/m^2$
• D. $83.14kN/m^2$

Answer 1

The correct option is D $83.14kN/m^2$


Active earth pressure at topmost layer of soil,
$k_{a}q=2C\sqrt{k_a}$
$\Rightarrow q=\frac{2C}{\sqrt{k_a}}=\frac{2\times 24}{\sqrt{1/3}}=83.144kN/m^2(\because k_a=1/3$ for $\varphi ={30}^{\circ })$