Shear band analysis based on a strain-gradient hypoplastic model

Localized deformation is commonly observed in granular materials, yet it remains significant challenges for constitutive modeling and numerical simulation. This study extends a hypoplastic model for shear band analysis in granular materials by incorporating a second-order gradient of the strain rate into its nonlinear tensorial function. The extended model keeps the conciseness of hypoplastic framework while introducing a length scale to capture the finite shear band thickness in the post-localization regime. This leads to improvements over the original non-gradient model in shear band analysis. Numerical simulations of simple shear tests demonstrate the model's capability to reproduce finite-thickness shear bands in granular materials with inhomogeneous initial void ratio distributions. Compared to the existing gradient models, the extended model shows superior performance in analyzing realistic shear band problems with rotation.