Question

A slope is to be constructed at an inclination of 30° with the horizontal. What will be the safe height of the slope at factor of safety of 1.5? The soil has the properties: c = 15 k N/m^2, φ=22.5° and γ = 19 k N/m^3.

(a) 11.5

(b) 20.5

(c) 12

(d) 18.64

This question was posed to me in an interview for job.

The doubt is from Taylor’s Stability Number and Curves topic in chapter Stability of Slopes of Geotechnical Engineering II

Answer 1

The correct choice is (a) 11.5

For explanation: The mobilized frictional angle φm is given by

φm = φ/F = 22.5/1.5 = 15°

For, i = 30° and φm = 15°, Sn =0.046

Now H = c/F γ Sn = 15/(0.0046×1.5×19) = 11.5 m.