Abstract

Physics tends to deal with point particles, continua, repeating patterns, neat formulae and symmetries. Granular systems sit in the awkward middle ground – grains are too complex and too numerous to model individually, yet too large and too few to be called a continuum. As such, they are a treasure trove for experimentalists, as feeding phenomenological models with the right data is still arguably our best route forward.

Looking at the very high-rate response of granular systems is fruitful both as an applied exercise, with applications ranging from earthquakes and asteroid impacts to defence, and as a purely scientific endeavour. At very high stresses, the complexities of compaction behaviour can be ignored, and standard thermodynamics describes the system rather well. Therefore, by gradually reducing the compaction stress and strain rate, we may have a handle for gradually ‘turning on’ the huge range of interconnected phenomena associated with granular systems.