DEM Simulations of Energy Dissipation in Sand under Static and Cyclic Loading

Abstract

Abstract In this study, numerical simulations by the discrete element method were carried out to examine the characteristics of energy dissipation in sand. In the simulations of static biaxial tests of loose and dense samples, it was found that the applied boundary work is either stored in the strain energy or dissipated through interparticle friction when viscous energy loss is not considered. At the critical state, the boundary work balances out the frictional loss and the strain energy ceases to increase. The release of frozen strain energy can be readily seen in the dense sample when the sample is sheared to dilation and under a strain softening response. In the simulations of cyclic simple shear tests at small strains from 6 × 10−6 to 1.5 × 10−4, both frictional and viscous energy losses were considered. The simulated damping ratio and associated shear modulus can be obtained from two methods: traced energy and the resulting hysteresis loop. These two methods render almost identical results. The simulation can reproduce similar responses like the experimental findings in both shear modulus and damping ratio at different confining pressures, strain levels, and strain rates. It is found that not only the lost energy but also the stored energy, which is related to the associated shear modulus, can significantly affect the response of the damping ratio. In addition, the frictional loss mainly takes place in the weak force network, but the viscous energy is quite evenly distributed in the strong and weak force networks.