Transition of shear flow for granular materials in a numerical ring shear test

摘要

The shear flow behaviors of granular materials exist widely in natural events. Ring shear tests based on the discrete element method were carried out to study the effects of shearing rate on the transition of quasi-static and slow flow phases of granular materials. The simulated results indicated that the shear stress and normalized volume increase linearly with the square of the shearing rate, and the two corresponding critical shearing rates are the same. Through the analysis of the mu(eff) (I) rheology model, the micro-mechanism of the transition between the quasi-static and slow flow phase has been discussed quantitatively. Additionally, the critical shearing rate under different normal stress and rolling resistance friction coefficient were tested. It is found that the critical shearing rate augments with the increase in normal stress. However, it does not change with the increase of the rolling resistance friction coefficient of granular materials. The above work on the flow phase transition of granular materials can be helpful to study the mechanism of the starting stage of geological disasters, such as landslides and debris flows.