An anisotropic elastoplastic strong discontinuity model for shear failure in anisotropic rock masses

In this paper, we propose a noval anisotropic elastoplastic strong discontinuity-FEM (SD-FEM) for analyzing the complete progressive shear failure process in anisotropic rock masses. The deformation property preceding slip is described with an elastoplastic formulation incorporating the microstructure tensor approach. Anisotropic discontinuous bifurcation analysis is conducted to judge the initiation conditions and propagation direction of slip lines. Furthermore, a derived anisotropic stress-displacement relation on the discontinuity is utilized to describe the post-failure response asscociated with slip. Two numerical examples, namely the uniaxial compression test of anisotropic rock masses and the loading problem of the anisotropic rock slope, are used to demonstrate the remarkable capabilities of the anisotropic elastoplastic SD-FEM model. It is illustrated that this model can not only reflect the anisotropic mechanical characteristics of rock masses but also accurately simulate the complete progressive failure process, spanning from uniform deformation to sliding failure. Notably, it is observed that the magnitude of slip (i.e., discontinuous displacement) exhibits a linear increase with the vertical load, highlighting the elastic-brittle deformation characteristics of rock masses. Moreover, the eigenvalues of the global stiffness matrix remain positive even in the softening stage, which enables the numerical calculation to proceed and ensures the mesh-independent numerical solutions, indicating that the anisotropic SD-FEM can regularize the ill-posedness of the boundary value problem when strain softening occurs.