Effect of Surface Obtrusions on Creep and Flow of Granular Piles

Despite their apparent simplicity, granular systems—dry, rigid grains interacting via contact forces—exhibit complex collective behaviors. Key challenges include understanding their rapid transitions between solid-like and fluid-like states and the heterogeneous way forces are distributed among grains. Our research investigates granular failure and creep: the slow, subsurface rearrangement of grains driven by applied stress and disordered interactions. We employ photoelastic techniques to probe the structure and dynamics of creep in quasi-2D granular piles down to the single-grain level. By instigating creep with controlled disturbances, we track the evolution of the contact force network and grain rearrangements to identify signatures of failure. A key focus is the influence of surface topography; we found that a non-flat base significantly reduces creep and failure events within the pile. This suggests surface texturing is a viable method for controlling the stability and flow of granular materials.