Stress-Induced Flow-Arrest Transitions in Frictional Granular Materials

Using discrete element simulations, we study the mechanical response of frictional granular materials that are subjected to homogeneous normal and shear stresses. Depending on the applied stress state, such materials either flow toward a steady or so-called critical state, or creep toward a statically stable arrested state. The transition from creep to flow for increasing stresses is characterized by increased fluctuations in the bulk strain rate, and increased dilation, indicating mechanical instability in the vicinity of this transition. Extensive simulations are performed to characterize the static yield stress of such frictional granular materials. A phase diagram mapping the boundary between flowing and arrested states is developed for a wide range of applied stresses, and is found to be strongly dependent on the inter-granular Coulombic friction. Microstructural analyses of the granular fabric highlight direct connections between continuum $\mu(I)$ rheology and mechanics of the so-called shear-jammed state. Such bulk measurements provide essential input towards the development of continuum models for granular mechanics and flow.