The evolution of shear bands in sand: Numerical investigations based on an elasto-plastic cosserat continuum approach

Abstract

This research is focused on the numerical investigations of the evolution of shear bands and polar effects within a planar layer of cohessionless and dry sand material under shearing. In this regard, micro-polar (Cosserat) continuum is used to account for micro-rotations, couple stresses and size effect in sand. In particular, extending the non-polar version of the employed elasto-plastic soil model is presented within the framework of Cosserat continuum. Non-linearity is considered in constitutive relations and geometry for the finite element implementation. It is demonstrated that strain localization with a finite thickness occurs under large quasi-static shearing. Location, thickness and evolution of strain localization are strongly affected by the rotating resistance of boundary grains of sand layer and the boundary conditions of entire system. The localization patterns are different within finite and infinite shear layers, depending on the prescribed lateral boundary conditions.