Question

In case of cohesive backfill, the total passive pressure is _________

(a) Pp=\(\frac{1}{2}\) Kp γH^2+2cH tanα

(b) Pp=γH^2+2c tanα

(c) Pp=Kp γH^2-2c tanα

(d) Pp=Kp H^2-2c tanα

This question was addressed to me in a job interview.

This interesting question is from Passive Earth Pressure: Rankine’s Theory in division Failure Envelopes & Earth Pressure of Geotechnical Engineering II

Answer 1

Right option is (a) Pp=\(\frac{1}{2}\) Kp γH^2+2cH tanα

The explanation: The pressure intensity pp for a cohesive soil is given by,

pp=Kp γz+2c tanα,

The total earth pressure P0 at rest per unit length is,

Pp=\(\int_0^H\)Kp γz+2c tanα.dz

∴ Pp=\(\frac{1}{2}\) Kp γH^2+2cH tanα.