Visualizing force chains in clogged silos*

Despite the importance of clogging of particles in a multitude of industrial processes and natural systems, our understanding of why and how materials clog is relatively poor. Specifically, we consider clogging by the formation of stable arches at silo openings; our insight into the precursors and mitigation measures of these clogs is currently limited. By performing experiments using photoelastic techniques on particles in a hopper setup, we are able to analyse clogging events of two-dimensional dry granular materials. The distribution of forces is precisely monitored at the silo output and surrounding areas, allowing us to witness what occurs before, during, and after clogging. With high temporal and spatial resolution, we quantitatively investigate patterns in the force network that precede clogging events and see how the residual forces impact the probability of subsequent clogs. This development in our understanding of the role of force networks in clogging could enable us to predict more effectively when clogs will occur.