Footprints in sand: the response of a granular material to local perturbations

Phys Rev Lett. 2001 Jul 16;87(3):035506. doi: 10.1103/PhysRevLett.87.035506. Epub 2001 Jul 2.

Abstract

We experimentally determine ensemble-averaged responses of granular packings to point forces, and we compare these results to recent models for force propagation in a granular material. We use 2D granular arrays consisting of photoelastic particles: either disks or pentagons, thus spanning the range from ordered to disordered packings. A key finding is that spatial ordering of the particles is a key factor in the force response. Ordered packings have a propagative component that does not occur in disordered packings.