Effective stress based stability analysis of normally consolidated clays

Abstract

This article discusses undrained effective stress stability analyses on normally consolidated soft clay. A key issue in such analyses is that the yield induced pore pressure is properly accounted for. Yielding of natural clays is affected amongst other factors on the shape and size of an anisotropic yield surface and the deformation properties of the clay, including creep. These then have a large effect also on the undrained capacity of the soil. The implementation of yield induced pore pressure into stability analyses conducted by both limit equilibrium method (LEM) and finite element method (FEM) is presented. Calculation examples are given for a full scale embankment failure experiment using various methods to include the yield induced pore pressure. It is shown that it is possible to account for such effects even in simple LEM analysis to obtain a realistic failure load, while in advanced FEM analysis it is possible to also account for time effects.