CYCLIC HARDENING BEHAVIOR AND ENERGY DISSIPATION OF GRANULAR MATERIALS WITH DIFFERENT PARTICLE SIZE DISTRIBUTIONS

Granular materials exhibit cyclic hardening behavior under cyclic loading. However,there are few studies on the mechanistic explanation of cyclic hardening behavior at the macro-micro scale. In this paper,the cyclic triaxial test DEM simulation is carried out to study the cyclic hardening behavior of granular materials with different particle size distribution under cyclic loading. The evolution of (axial) average deformation modulus and energy dissipation due to sliding contact is analyzed. The results show that the average modulus increases gradually and tends to asymptotic values as the cyclic loading progresses. The energy dissipation of each cycle does not always decay with the increase of cycles,but has a threshold. The increase index of the average modulus and the decay index of energy dissipation are similar in magnitude(about 0.6)for all the specimens with different particle size distribution,indicating that whether the deformation modulus or the normalized energy dissipation are used,the results are consistent when describing the cyclic hardening behavior. The energy dissipation caused by sliding contact at the microscale is mapped to the average modulus at the macroscale. The larger the average particle size of the granular assembly,the larger the average modulus,and the earlier the completion of the energy dissipation process. However,the corresponding energy dissipation threshold difference under different particle size distributions is small,basically maintained at a constant of 0.15.