Abstract:The strength and deformation characteristics of rockfill materials were influenced by particle breakage. However, most of the studies on particle breakage were under static loading conditions. To investigate the effect of particle crushing on the dynamic characteristics of rockfill materials under small strain conditions, the discrete element method was selected to simulate the dynamic response of granite rockfill materials under different confining pressures. The hexagonal closed packing with different random combinations was used to simulate irregular particle shape. The fragment replacement method was selected to simulate particle crushing. The influence of porosity on dynamic elastic modulus was studied, and the particle breakage law and the frequency distribution of coordination number during cyclic loading were analyzed. The simulation results were in good agreement with laboratory test results. This indicated that the numerical model could reproduce the dynamic deformation characteristics of rockfill materials under different confining pressures. Particle breakage increased the dynamic strain and decreased dynamic elastic modulus under the same confining pressure and dynamic stress. During cyclic loading, the effective coordination number decreased slowly. The sample with particle breakage produced more mechanically unstable particles, and the decrease of effective coordination number was more significant when compared with the sample without particle crushing. Particle crushing accelerated the decay rate of the dynamic elastic modulus with the increase of dynamic strain. The sample with lower porosity had higher effective coordination number and better mechanical property. Under the same stress condition, the sample with lower porosity had larger maximum dynamic elastic modulus and went through less particle breakage. The dynamic elastic modulus decayed slowly with the dynamic strain increasing. The maximum dynamic elastic modulus for the sample with lower porosity was about 1.2 times of that for the sample with larger porosity. The maximum dynamic elastic modulus was mainly related to the effective average principal stress and porosity. The empirical formula proposed by Hardin could be used to describe the relationship between the maximum dynamic elastic modulus, void ratio and average effective principal stress. The results were helpful to understand the deformation law of coarse granular materials and provided reference for the simulation of particle crushing behavior under cyclic loading.