Abstract:This paper investigates shear strength of granular materials with inherent fabric anisotropy. Most previous studies have described strength of these materials in the principal stress space, and the orientation of the bedding plane with respect to the principal stress directions was used as the reference geometrical descriptor of inherent fabric. The present study has found that it is theoretically more convenient and practically more useful to use instead the inclination angle of the bedding plane with respect to the shear plane for the same purpose. Direct shear tests and biaxial compression tests with different loading directions with respect to the bedding planes were simulated with discrete element method (DEM) models consisting of ellipse-shaped particles. Key mechanical behaviors of natural sands reported in the literature were successfully captured in the numerical simulation. A shear failure criterion was determined as a function of the inclination angle based on the direct shear simulation results, and was used to successfully predict the results of the biaxial compression simulations. Microstructural inspection of deformation and strain localization of the biaxial compression simulations found that the proposed shear failure criterion can reasonably predict the orientations of the initial failure planes. It was also discovered that shear bands in directions conjugate to the initial failure plane orientations can develop and dominate specimen deformation at larger strain levels. Considering the availability of biaxial compression test equipment and historical data, two methods for back-calculating inclination angle-dependent shear strength from biaxial compression results were proposed, and validated using DEM simulation results.