Question

If the angle of internal friction decreases, then Ka  ___________

(a) decreases

(b) increases

(c) equal to zero

(d) does not change

I have been asked this question in homework.

Query is from Active Earth Pressure: Rankine’s Theory in portion Failure Envelopes & Earth Pressure of Geotechnical Engineering II

Answer 1

Right option is (b) increases

Explanation: Since the coefficient of earth pressure for active state of plastic equilibrium is given by,

\(K_a=\frac{1-sinφ}{1+sinφ}.\) Therefore, from the equation it is clear that as the angle of internal friction decreases, then Ka increases.