The figure shows the soil profile at a site where you plan to lower the water table. You have results from two consolidation tests, one from the upper 12 ft thick over-consolidated crust, and another from the lower 32 ft thick normally consolidated zone. You plan to lower the water table from its current 12 ft depth to 20 ft below ground surface. The consolidation properties for each layer are shown. Assume full capillarity.

(a) Compute σ’v the in the middle of each layer before and after the water table is lowered.

Stiff clay, y = 120 pcf Cr. = 0.029, Co. = 0.178, o, = 1650 psf 20 Soft clay, Y = 118 pcf Cr. = 0.034, Cc. = 0.185 44 Depth (ft)