Question

If the time required for 60% consolidation of a remoulded soil sample of clay with single drainage is 't', then what is the time required to consolidate the same sample of clay with the same degree of consolidation but with double drainage?

• A. 4t
• B. 2t
• C. t/2
• D. t/4

Answer 1

The correct option is D t/4

For same degree of consolidation,

$\frac{t_1}{t_2}={\left(\frac{d_1}{d_2}\right)}^2$

Single drainage $t_1=t;d_1=H$
Double drainage $t_2=?,d_2=H/2$

$\therefore t_2=t\times {\left(\frac{H/2}{H}\right)}^2=\frac{t}{4}$