Question

For a cohesion less soil, the total passive pressure Pp at a depth H is ___________

(a) Pp=\(\frac{1}{2}\) Kp γH^2

(b) Pp=γH^2

(c) Pp=Kp γH^2

(d) Pp=Kp H^2

The question was asked in an interview for job.

This intriguing question originated from Passive Earth Pressure: Rankine’s Theory topic in section Failure Envelopes & Earth Pressure of Geotechnical Engineering II

Answer 1

Right choice is (a) Pp=\(\frac{1}{2}\) Kp γH^2

To explain I would say: The pressure intensity pp is given by,

pp=Kp γz,

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

Pp=\(\int_0^H\)Kp γz.dz

∴ Pp=\(\frac{1}{2}\) Kp γH^2.