"A 10-m depth of sand overlies an 8-m layer of clay, below which is a further depth of sand. For the clay, mv=0.83m2/MN and cv=4.4m2/year. The water table is at surface level but is to be lowered permanently by 4 m. Calculate the final settlement due to consolidation of the clay, assuming no change in the weight of the sand."
Here is their solution:
What I don't understand is why the change at the top of the clay layer is different from that at the bottom of the clay layer...? And why does the pore water pressure at the bottom of the layer stay constant?
Thanks for your help!