The Effects of Grain-Scale Properties on the Rapid Compaction of Sand

We review recent experimental efforts at the Cavendish Laboratory regarding the dynamic response of silica sand under a variety of loading rates and geometries - principally plate impact and ballistic penetration. By studying the response of several similar sands in multiple loading scenarios, significant insight has been gained into the key phenomena controlling response. While dynamic behavior is largely controlled by grain-grain contact phenomena, there is a shift from shear behavior and lubrication dominating low rates (where long-range force chains dominate), to compression and stress focusing at high rates - with the transition occurring around the sound speed of the granular material in question.