Stress distributions in a two dimensional granular material

We have experimentally studied the distribution of stress within a two-dimensional granular material, composed of photoelastic optical fibers of uniform size, contained in a biaxial shear cell. In this material as in other granular materials, stress is concentrated along branching chains of stressed grains. These stress chains determining when the material will be rigid and when it will fail. Defects in the grain packing occur when the load is changed on the biaxial shear cell, and these defects largely determine the locations and orientations of the stress chains.