Influence of both anisotropic friction and cohesion on the formation of tension cracks and stability of slopes

A modified logarithmic-spiral limit equilibrium procedure is proposed to rigorously determine the critical failure mechanism and stability of slopes comprised of soils where both friction angle and cohesion demonstrate anisotropic shear strength. The influence of both cohesion and friction anisotropy has not been explicitly considered using the logarithmic spiral approach. This procedure allows for the critical failure mechanism and stability to be determined in simplified soil strata independent of the internal statical assumptions associated with other rigorous slope stability approaches. The unique geometry of the logarithmic spiral enables direct assessment of the normal stress distribution acting along the failure surface using a modified analytical solution. This computed normal stress distribution enables evaluation of tensile stresses along a slip surface, thus providing a rational means of explicitly determining the depth of the tension crack for both isotropic and anisotropic conditions, which is novel. Within this study, a procedure is proposed to study the influence of cohesive and frictional anisotropy on tension crack depth and slope stability. In addition, to understand the impact of an often-realistic variable on anisotropic stability, the orientation of the plane of weakness due to geologic conditions is studied over the range from 90 degrees to -90 degrees .