Question

The Belli equation of lateral pressure of cohesive soil is ____________

(a) pa=γzcot^2 α-2c cot⁡α

(b) pa=γzcot^2 α+2c cot⁡α

(c) pa=-2c cot⁡α

(d) pa=γzcot^2 α/2c cot⁡α

I got this question in an interview for internship.

The above asked question is from Active Earth Pressure of Cohesive Soils topic in division Failure Envelopes & Earth Pressure of Geotechnical Engineering II

Answer 1

Correct choice is (a) pa=γzcot^2 α-2c cot⁡α

The explanation is: Since the principal stress relationship on a failure plane is given by,

σ1=2c tan⁡α+σ3 tan^2 α,

 σ1=γz and σ3=pa,

∴ γz=2c tan⁡α+pa tan^2 α

∴ pa=γzcot^2 α-2c cot⁡α.