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In: Civil Engineering

A Normally Consolidated 10 Ft. clay layer is surcharged, which causes a decrease in thickness. The...

A Normally Consolidated 10 Ft. clay layer is surcharged, which causes a decrease in thickness. The coefficient of consolidation is 0.16 ft^2/day and the time factor is 1.2 for U=50%. The clay layer is confined between 2 layers of dense sand. The time (days) required for 50% consolidation is most nearly?

This is a question from a practice FE exam. The reference book and the solution to this leaves out some information. The equation is Tv=Cv(t)/Hdr^2)

The solution has Hdr=5 ft. Why is that?

Solutions

Expert Solution

The one dimension consolidation test is based on the drainage condition of soil. When a clay layer is confined between two pervious layers as given in problem, it means that the water particle can move in both direction to get drained out, resulting in effective depth of clay layer to half. In such cases drainage path Hdr=(H/2)= (10/2)= 5ft.

The same is explained in attached photographs.

Thanks.

Ally Wells answered 10 months ago
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