Question

Question Three: Chose answer (3 Mark)
The time required for 25% consolidation of a 40mm thick clay layer, drained on both ends, in the laboratory is 4 min. How long, in days, will take for a 2-m thick clay of the same clay in the fiel under the same pressure increment to reach 25% consolidation? The soil mass in the field is sandwiched between two thick layers of gravel, as shown.

Answer 1

The time required for consolidation is proportional to the square of the thickness of the clay layer.
Therefore, the proportionality constant can be calculated as follows:
t1/t2 = (H1^2)/(H2^2)
Substitute the values given:
4 min/t2 = (40mm)^2/(2000mm)^2
t2 = 4 min * (2000 mm)^2 / (40 mm)^2
t2 = 20 days
Therefore, it will take 20 days for the 2m thick clay layer in the field to reach 25% consolidation.