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