Three-dimensional stability analysis of slopes in hard soil/soft rock with tensile strength cut-off

Many collapse analyses of slopes in soils or soft rocks use the classical Mohr-Coulomb yield function to define the strength of geomaterials. In the presence of bonded particles and grains, this function predicts uniaxial tensile strength and even greater isotropic tensile strength. Testing for material properties, however, is typically carried out in the compressive regime; the tensile strength is then burdened by uncertainties, as it is a result of extrapolation of test results into the tensile regime. A three-dimensional limit analysis of slopes is presented with the geomaterial described by a yield surface with tensile strength cut-off. The multiplicity of admissible collapse mechanisms is enriched, as the tension cut-off allows construction of mechanisms that include rupture modes. Stability factors for slopes with tensile strength cut-off are reduced compared to those based on the classical Mohr-Coulomb strength envelope, with the largest drop for steep slopes subjected to seepage. The stability factor for a 70-degree slope subjected to seepage can be reduced by as much as 69% when tensile strength cut-off is considered.