Question

In Fellenius method for small values of angle of internal friction of soil, the critical arc passes ________________

(a) through the toe of the slope

(b) above the toe of the slope

(c) below the toe of the slope

(d) anywhere near the toe of the slope

I had been asked this question during an interview.

My doubt stems from Stability of Earthen Slopes topic in section Earthen and Rock Fill Dams of Irrigation Engineering

Answer 1

The correct answer is (c) below the toe of the slope

The explanation: The critical arc passes below the toe of the slope for small values of angle of internal friction of the soil (0° to 15°) if the angle of inclination is less than 53°. For large values of internal friction angle, the critical arc passes through the slope.