Question

A cohesionless soil forms a natural infinite slope at \(25^\circ\). If the effective friction angle is \(30^\circ\), determine the factor of safety (round off to 2 decimals).

Hint:

For dry sand slopes: \(F_s = \tan \phi / \tan \beta\).

Answer 1

Correct Answer: 1.22

For infinite slope in dry cohesionless soil:
\[ F_s = \frac{\tan \phi}{\tan \beta} \] \[ F_s = \frac{\tan 30^\circ}{\tan 25^\circ} \] \[ F_s = \frac{0.577}{0.466} = 1.24 \]