The excavation was being done for a foundation trench in a plastic clay having a unit weight of 2.3 gm/cc. When the depth of excavation reached 4 meters, it failed. On the Assumption that ☀ = 0, the value of the cohesion of the clay is?

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The foundations supporting two columns of a building are shown in Figure E9.16. An extensive soil investigation was not carried out, and it was assumed in the design of the foundations that the clay layer had a uniform thickness of 1.2 m. Two years after construction the building settled, with a differential settlement of 10 mm. Walls of the building began to crack. The doors have not jammed, but by measuring the out-of-vertical distance of the doors, it is estimated that they would become jammed if the differential settlement exceeded 24 mm. A subsequent soil investigation showed that the thickness of the clay layer was not uniform but varies, as shown in Figure E9.16. The owners would like to get an estimate of the expected total differential settlement and how long it will take before the doors become jammed. 780 kN| 780 kN Foundation A Foundation B 1.5 m x 1.5 m 1.5 m x 1.5 m Sand. 1.4 m 3 m 2.8 m 1.2 m Clay, m, = 0.7 m²/MN Gravel FIGURE E9.16