Experimental evidence of structural development inside shear bands in sands

Abstract

We show experimental evidence of vortices emanating from collapsed force chains in shear bands in real sands. From digital image-based local displacement data, a systematic, spatial pattern in kinematic data fields appears at the softening-critical state transition. By subtracting a linear shear displacement field from the observed non-affine displacement field, vortices appear and coordinate with the observed kinematics. We note differences in the vortex patterns observed in our sands from those observed in simulations on “ideal” granular materials, and discuss the fate of these vortices.