Question

A clay layer 5 m thick in field takes 300 days to attain 50% consolidation with condition of double drainage. If the same clay layer is underlain by hard rock then the time taken to attain 50% consolidation will be

• A. 300 days
• B. 600 days
• C. 900 days
• D. 1200 days

Answer 1

The correct option is D 1200 days

Since $T_v=\frac{C_{v}t}{d^2}$, therefore for same values of $T_v$ and $C_v$, t is proportional to $d^2$ where d is length of drainage path. Therefore the time taken in single drainage will be four times that in the double drainage.