An exploratory drill hole was made in a stiff saturated clay $($see figure below$).$ The sand layer underlying the clay was observed to be under artesian pressure. Water in the drill hole rose to a height of $12$ ft above the top of the sand layer.

Part a $(5\%)$ : Calculate ${}_{\text{s}\text{a}\text{t}}(l\frac{b}{f^3})$ for the clay layer.

Part b $(5\%)$: Calculate the pore water pressure at point $A,u_A(l\frac{b}{f}{t}^2).$

Part c $(5\%)$: If an open excavation is to be made in the clay, how deep can the excavation proceed before the bottom heaves?

$=2\mathrm{.}72$

sture content $=w=35\%$

Sand