Question

Active earth pressure per meter length on the retaining wall with a smooth vertical back as shown in the given figure will be

• A. 81 t
• B. 27 t
• C. 2 t
• D. 1 t

Answer 1

The correct option is B 27 t

Active earth pressure coefficient
$K_a=\frac{1-\sin \varphi }{1+sin\varphi }=\frac{1-sin{30}^{\circ }}{1+\sin {30}^{\circ }}=\frac{1}{3}$
Active earth pressure per unit length
$=\frac{1}{2}{K}_a\gamma H^2=\frac{1}{2}\times \frac{1}{3}\times 2\times 9\times 9=27t/m$