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 μ_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.

粒状材料的剪切流动行为在自然事件中广泛存在。进行了基于离散元法的环形剪切试验，研究了剪切速率对粒状材料准静态相和慢流相转变的影响。模拟结果表明，剪切应力和归一化体积随剪切速率的平方线性增加，并且两个相应的临界剪切速率相同。通过对分析μ _EFF（我）流变模型，对准静态相和慢流相之间的过渡过程的微观机理进行了定量讨论。另外，测试了在不同法向应力和滚动阻力摩擦系数下的临界剪切速率。发现临界剪切速率随着法向应力的增加而增加。但是，它不会随着粒状材料的滚动阻力摩擦系数的增加而变化。以上关于颗粒状物料流相转变的研究工作，有助于研究滑坡，泥石流等地质灾害起步阶段的机理。