A cut slope was excavated in a saturated clay with a slope angle, ( = 48°, with the horizontal. Slope failure occurred when the cut reached a depth of 10 m. Previous soil explorations showed that a rock layer was located at a depth of 14 m below the ground surface. Assuming an undrained condition and ( = 17 kN/m3:
a. Determine the undrained cohesion of the clay (Figure 15.13).
b. What was the nature of the critical circle?
c. With reference to the top of the slope, at what distance did the surface of the sliding intersect the bottom of the excavation?