Question

If at interface of dissimilar soils, k1=9×10^-7 cm/s and k2=4×10^-7 cm/s. The deflection of flow lines at interface has θ1=30°, then θ2 will be _______

(a) 12.39°

(b) 13.39°

(c) 14.39°

(d) 15.39°

I got this question in an internship interview.

My question is from Seepage through Anisotropic Soil topic in division Seepage Analysis of Geotechnical Engineering I

Answer 1

The correct answer is (c) 14.39°

Easiest explanation: Given,

k1=9×10^-7 cm/s

k2=4×10^-7 cm/s

θ1=30°

since   \(\frac{k_1}{k_2} = \frac{tanθ_1}{tanθ_2}\)

\(\frac{9×10^{-7}}{4×10^{-7}} = \frac{tan30}{tanθ_2}\)

∴ θ2=14.39°.