Numerical study on energy transformation in granular matter under biaxial compression

Granular matter consists of a large number of clearly distinguishable particles. Examples include coarse grain soil, rockfills and so on in which neighboring particles contact with each other and form skeletons to support gravity and other external loadings. Once the contacts are losing or re-creating, various kinds of energy, such as elastic energy, kinetic energy, would transform into each other, while some of them would dissipate if sliding occurs. In this paper, a biaxial test on a 2D granular sample is numerically simulated by using the software of PFC2D. The fluctuation of strain-stress relation is observed and considered as the stick-slip motion of force chain, i.e. destructing and re-constructing of force chain. Every kind of energy is calculated and analyzed at different stress-strain stages. They are further compared with force chain network configurations. It is found that as shear band fully developed, all the boundary work is almost dissipated within shear band. These findings emphasize the importance of study on mesoscale structure dynamics, such as particle and force chain re-arrangement.