Loading rate effect on the strength of granular material considering particle rotation

A variety of factors have significant influences on the strength of a granular system, such as the loading rate. However, the effect of loading rate on the strength of granular material systems has not attracted extensive investigations. In this study, based on the rate-state shear strength theory of granular materials, the general frictional coefficient for the granular material system in 2D space is obtained by introducing the loading rate and considering the particle rotation. A 2D discrete element simulation of spherical glass beads system with different combinations of confining pressures and loading rates is carried out by PFC2D. The results show that the me-chanical behavior of the granular material system is more affected by the high loading rate and the critical loading rate is confirmed. The response of rotation ratio and other key parameters appearing in the proposed theory are further obtained. The theoretical predictions are also compared with the numerical simulations and good agreements have been observed. It is believed that the theoretical model proposed in this work can provide a helpful path in investigating the strength of granular materials and offer a method to determine the strength of granular materials for practical engineering projects.