Question

A clay sample 24mm thick takes 20 minutes to consolidate 50% with double drainage. The field clay layer from which sample was obtained takes 386 days to consolidate 50% with double drainage. Find the depth of the clay layer in the field.

(a) 4m

(b) 7m

(c) 3m

(d) 2m

The question was posed to me during an internship interview.

Asked question is from Consolidation Problems topic in section One Dimensional Consolidation of Geotechnical Engineering I

Answer 1

Correct answer is (a) 4m

The explanation: Given,

t1= 20 min

t2= 386 days

d1= 2.4/2 = 1.2 cm

since, \(\frac{t_2}{t_1} =(\frac{d_2}{d_1})^2\)

therefore \(d_2 = d_1 \sqrt{\frac{t_2}{t_1}}=1.2\sqrt{\frac{386×60×24}{20}}=200cm=2m\)

since double drainage is allowed, the depth is 4m.