Prediction of Progressive Failure in Heavily Overconsolidated Slope

Abstract

A theoretical solution for the subcritical growth of a crack in a quasi‐brittle solid is applied to predict the time for progressive failure to develop in a heavily overconsolidated clay slope. The solution utilizes the principles of delayed fracture in a linear viscoelastic plastic quasi‐brittle material to determine the initiation time and rate of propagation of the failure surface in terms of the loading, material properties, and boundary conditions. A hypothetical example of a slope 17 m high in an overconsolidated soil, using the actual properties of an overconsolidated soil, is given to illustrate the method of solution. An excavation at the toe of the slope causes an overstressed zone from which a crack is assumed to be initiated along the failure surface. The initiation time and the rate of crack propagation are in accordance with the theory of fracture mechanics, in which creep plays a dominant role. The residual shear strength is used along the crack surface and the peak shear strength is used along the remainder of the failure surface to determine the factor of safety against slope‐stability failure.