Question

A clay sample 24mm thick takes 20 minutes to consolidate 50% with single 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) 800cm

(b) 500cm

(c) 600cm

(d) 480cm

I had been asked this question in an interview for internship.

I'm obligated to ask this question of Consolidation Problems in portion One Dimensional Consolidation of Geotechnical Engineering I

Answer 1

Right option is (a) 800cm

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

t1= 20 min

t2= 386 days

d1= 2.4 cm

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

therefore \(d_2 = d_1 \sqrt{\frac{t_2}{t_1}}=2.4\sqrt{\frac{386×60×24}{20}}=400cm=4m.\)

Since double drainage is allowed in field, the depth is 400×2= 800 cm.