Question

A clay sample in laboratory test has 24mm thickness. It is tested with double drainage and consolidated 50%. The clay layer from which sample was obtained is 4m thick. Find the time to consolidate 50% with double drainage.

(a) 365 days

(b) 386 days

(c) 750 days

(d) 150 days

This question was posed to me by my college director while I was bunking the class.

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

Answer 1

Right option is (b) 386 days

Explanation: Given, double drainage for both specimen and field,

t1=20 min

d1=24 mm/2 = 2.4 cm/2 = 1.2 cm

d2 =4/2 m 200cm

Since, for same degree of consolidation of 50%, Tv is same,

\(t∝\frac{d^2}{C_r}\)

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

So, \(t_2=t_1 (\frac{d_2}{d_1} )^2=20(\frac{200}{1.2})^2=365 \,days.\)