Failure potential of infinite slopes in bonded soils with tensile strength cut-off

Abstract

Infinite slope analyses are used in practice to assess the safety of slopes against shallow slides, with much of the soil mass moving parallel to a plane failure surface. Stability calculations typically involve the Mohr–Coulomb yield function, but the limitation on tensile strength is discussed and applied in stability considerations for bonded soils. Once the strength envelope is truncated in the tensile regime, the envelope becomes nonlinear and the normality flow rule admits deformation with large volumetric strains. For gentle slopes and in the absence of seepage, the difference in factors of safety calculated with and without tensile strength cut-off is small. However, in the presence of seepage and with increasing inclination of slopes, the difference becomes significant. As the deformation regime moves into the nonlinear portion of the yield envelope, application of the traditional definition of the factor of safety is not straightforward. If the strength envelope is truncated with a circular arc, then the envelope reduced by the factor of safety assumes an elliptical shape. The novelty in this paper is in presenting an analysis for bonded geomaterials with tensile strength cut-off, and indicating that tension cut-off can have a significant impact on the outcome of stability analysis for steep slopes subjected to seepage.