In a laboratory consolidation test on a representative sample of fine-grained so
ID: 1827575 • Letter: I
Question
In a laboratory consolidation test on a representative sample of fine-grained soil, the
original height of the doubly drained sample was 25.4 mm. The time for 50%
consolidation to take place was 9 minutes. The laboratory sample was taken from a soil
layer which is 12 m thick in the field, doubly drained, and is subjected to similar loading.
a. How long will it take until the layer consolidates 50%?
b. If the final consolidation settlement is predicted to be 18 cm, how long will it take
for a settlement of 4 cm to take place?
Explanation / Answer
a).
T= Cv*t/h^2
Cv= coefficient of consolidation
T= time factor
for 50% consolidation, T= pi*0.5^2/4 = 0.196
for lab test;
doubly drainage is given, h= 25.4/2= 12.7 mm= 0.0127 m
t= 9 minutes
therefore,
0.196=Cv*9/0.0127 = 2.766*10^-4 m^2/min or 4.6 mm^2/s
for field test,
h= 12/2/= 6 m
50% consolidation, T=0.196
0.196= 2.766*10^-4*t/6^2
t = 25509.76 minutes or 17.715 days.
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