A NUMERICAL INVESTIGATION OF THE STRUCTURE OF PERSISTENT SHEAR BANDS IN GRANULAR MEDIA

The structure of persistent shear bands in granular materials is investigated by numerically simulating an idealized assembly of two-dimensional particles. Flexible stress-controlled boundaries are used instead of periodic boundaries to avoid constraining the motion of particles within the shear bands. The displacement, volumetric strain, void ratio, rotation of the particles, rotation of their neighbourhoods and contact orientation are examined within the shear band. The volumetric strain determined from local deformation gradients is found to overestimate dilatancy. The particle rotations are related to the rigid rotation of their neighbourhoods. The importance of rotations inside shear bands justifies the micropolar description of granular materials.