Question

The passive earth pressure intensity is given by _______

(a) pp=γz cot^2 α

(b) pp=γz tan^2 α

(c) pp=γz sin^2 α

(d) pp=γz cos^2 α

The question was posed to me in semester exam.

I'm obligated to ask this question of Passive Earth Pressure: Rankine’s Theory topic in section Failure Envelopes & Earth Pressure of Geotechnical Engineering II

Answer 1

The correct answer is (b) pp=γz tan^2 α

To explain: In case of passive state of plastic state of equilibrium,

pp=σh=σ1, and σ3=σv=γz,

∴ for non-cohesive soils, σ1=σ3 tan^2 α,

∴ pp=γz tan^2 α.