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 single drainage. Find the depth of the clay layer in the field.

(a) 5m

(b) 2m

(c) 22m

(d) 16m

This question was posed to me in class test.

This question is from Consolidation Problems in division One Dimensional Consolidation of Geotechnical Engineering I

Answer 1

The correct answer is (b) 2m

Easiest explanation: Given, the sample has double drainage while the field layer has single drainage.

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