Question

For angle of internal friction of 250, the ratio of coefficient of passive and active earth pressure is __________

(a) 2

(b) 4

(c) 6

(d) 8

This question was addressed to me in unit test.

My question comes from Passive Earth Pressure: Rankine’s Theory in chapter Failure Envelopes & Earth Pressure of Geotechnical Engineering II

Answer 1

The correct answer is (c) 6

Best explanation: Given,

angle of internal friction φ=250,

∴ \(\frac{K_p}{K_a} =tan^4 (45°+\frac{φ}{2}) = tan^4 (45°+\frac{25}{2}),\)

Kp/Ka =6.