Question

The Belli equation at the ground surface is given by _________

(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

The question was posed to me during an interview for a job.

This interesting question is from Active Earth Pressure of Cohesive Soils topic in section Failure Envelopes & Earth Pressure of Geotechnical Engineering II

Answer 1

Correct option is (c) pa=-2c cot⁡α

Explanation: Since the Belli equation of lateral pressure of cohesive soil is given by,

pa=γzcot^2 α-2c cot⁡α,

at the ground surface, z=0,

∴ pa=-2c cot⁡α.