Question

The lateral pressure for cohesive backfill with surcharge q is ___________

(a) pa=γzcot^2 α-2c cot⁡α+qcot^2 α

(b) pa=γzcot^2 α+2c cot⁡α+cot^2α

(c) pa=-2c cot⁡α-cot^2 α

(d) pa=γzcot^2 α/2c cot⁡α

I had been asked this question during an online interview.

My question comes from Active Earth Pressure of Cohesive Soils topic in section Failure Envelopes & Earth Pressure of Geotechnical Engineering II

Answer 1

Right choice is (a) pa=γzcot^2 α-2c cot⁡α+qcot^2 α

Easy explanation: When the cohesive backfill carries a surcharge of q per unit area, then the lateral pressure is increased by Ka q. Since, Ka=cot^2α,

∴ pa=γzcot^2 α-2c cot⁡α+qcot^2 α.