The multiscale model for brittle granular materials generally involves three scales: elementary particles at the microscale

grains at the mesoscale

and grain piles at the macroscale. The multiscale model was created based on the discrete element method (DEM). To apply it to dynamic loading

parameters for two contact models and two bonding models were firstly analyzed

and connections between the micro and meso model parameters and the macro material constants were also discussed. Then

the dynamic multiscale model for quartz sand was created with the Hertz-Mindlin contact model and the parallel-bond model. Through selecting appropriate strength and local damping parameters

it is observed that the dynamic compression properties of the simulated sand agree well with the experimental results on quartz sand at both the meso and macro scale. With the calibrated model

the influence of the local damping mechanism which is closely related to dynamic loading

on the dynamic responses of the multiscale model was investigated. Results show that a higher damping level results in a stronger wave-attenuation ability of brittle granular materials. However

excessively high damping will result in an aberrant loading-velocity effect at both the meso and macro scale (the latter is actually the micro inertial effect induced by high damping). In addition

high damping can attenuate the waves emitted during the particle breakage process and reduce the breakage extent. At last

the multi-scale model was slightly modified and used to study the dynamic particle breakage property of brittle granular materials. The modified model can yield grain-size-distribution curves consistent with the experimental ones. Moreover

it can reveal the heterogeneous distribution of particle breakage at the space scale

which refers to the clustering phenomenon of microcracks caused by the interactions between the wave-producing and wave-attenuation mechanism in the particle breakage process.