Effect of Grain Shape on Creation of Vortex/anti-vortex- Structures in Granular Bodies Using Dem

Granular vortex structures (swirling motion of several grains around its central point) were frequently observed in experiments on granular materials and in calculations using the discrete element method (DEM). They became apparent when the motion associated with uniform (affine) strain was subtracted from the actual granular deformation. The dominant mechanism responsible for the vortex formation was the buckling of force chains [1], [2]. The collapse of main force chains lead to the formation of larger voids and their build-up to the formation of smaller voids [2]. The vortices have been mainly observed in shear zones [2], which are the fundamental phenomenon in granular bodies. However, a precise mechanism behind the vortex evolution and shear localization still remains elusive.