Stability charts for undrained clay slopes considering soil anisotropic characteristics

It is generally recognized that the stress-induced anisotropy of undrained cohesive soil has a significant influence on the factor of safety of slopes. In this study, a simplified method is proposed to evaluate the slope stability considering soil anisotropic shear strength. An advanced constitutive model is used to characterize the anisotropic behavior of strength and stiffness of cohesive soil caused by the rotation of principal stress direction. A series of finite element analysis is carried out using the strength reduction method to calculate the safety factor of the undrained clay slope. The stability chart developed by Taylor (1937) has been adapted to take into consideration the anisotropic conditions of the clay slope. The stability number and failure modes of undrained clay slopes with different geometries and depths to hard stratum can be quickly assessed using the proposed design charts. Additionally, the feasibility of replacing complex anisotropy analysis with average isotropic constant undrained strength is discussed. Different suggestions are proposed for gentle and steep slopes. Findings of the present study can be a helpful supplement to the existing slope stability assessment for unreinforced undrained clay slopes.