Elastoplastic Cosserat continuum model considering strength anisotropy and its application to the analysis of slope stability

Aiming at solving the problems of strength anisotropy and strain localization of cohesive soil, Pietruszczak's method, in which the microstructure tensor is combined with stress invariance, is developed to analyze the cohesion anisotropy and is introduced into the Drucker-Prager constitutive model under Cosserat continuum theory. A consistent algorithm of the corresponding constitutive model is derived. The characteristics of strength anisotropy and the reliability of the developed numerical method are verified by the experiments in laboratory. The importance and necessity of developing the numerical model with strength anisotropy under the framework of Cosserat theory are evaluated via simulation of a plane strain compression model. It indicates that the degree of the cohesion anisotropy has an important influence on the bearing capacity, and that the numerical model can overcome the ill-posedness of the mesh sensitivity and maintain the well-posedness of the strain localization problem. Furthermore, the effects of strength anisotropy and strain softening on the safety factor of the slope are analyzed via the gravity increase method. It is demonstrated that the Cosserat continuum model can effectively overcome the problems of mesh-dependence encountered by the classical continuum model and yield a reasonable safety factor with mesh refinement.