On progressive failure of sand considering fabric evolution with micropolar hypoplastic model

To study the progressive failure of sand considering the multi-scale and its fabric evolution, the fabric is used as the quantitative link from micro to macro, then the influence of fabric on the anisotropic critical state is adopted to establish a hypoplastic model, and the fabric evolution and micropolar theory are employed to describe the mesoscopic mechanism of local deformation, finally, the simulations of discrete element methods (DEM) and finite element methods (FEM) is coordinated to reproduce the progressive failure. In the DEM biaxial simulations, the distribution of the contact normal is quantitatively determined by the novel orthotropic fabric tensor, and the difference in particle shapes and sample position showed that the fabric evolution is obvious, especially inside and outside the shear band, and before or after the shear band penetration. The fabric evolution of DEM is implanted into the corresponding location of the FEM sample, the results indicate that the macro-meso incorporation hypoplastic model can effectively describe strain localization evolution and progressive failure. The internal length of micropolar theory and particle size are identified as the main factors influencing the shear band thickness. The anisotropic fabric influences the shear band patterns, with circular and elliptical particles tending to form an "X-shape" shear band, while square and triangular particles tend to form a "L-shape" shear band.