Case 1: Formation Full Plastic Failure Zone Below the Bottom Cut. of B H of

Case 1: Formation of Full Plastic Failure Zone Below the Bottom of Cut. Figure 20.31 (a) is a vertical section through a long cut of width B and depth H in saturated cohesive soil (l/J = 0). The soil below the bottom of the cut is uniform up to a considerable depth for the formation of a full plastic failure zone. The undrained cohesive strength of soil is c. The weight of the blocks of clay on either side of the cut tends to displace the underlying clay toward the excavation. If the underlying clay experiences a bearing capacity failure, the bottom of the excavation heaves and the earth pressure against the bracing increases considerably.