2. (5 pts) An exploratory drill hole was made in a saturated stiff clay shown below. It was observed that the sand layer underlying the clay was under artesian pressure (i.e., upward seepage). Water in the drill hole rose to a height of 4 m above the top of the sand layer. If an open excavation is to be made in the clay, how deep can the excavation proceed before the bottom heaves? 8 m H Saturated Clay e=0.86 G₁ = 2.7 Sand ilk 4 m

Fig: 1