Local failure of gradually tilted cohesive granular beds

In the presence of inter-particle cohesion, gradually inclining a rectangular bed of particles can lead to localized mobilization of grains on the downstream edge. Experiments of such failure are observed to display a loop-like structure on the top surface from where material is mobilized. By controlling the amplitude of cohesion, the bed geometry, and the grain size, we show that such features are characteristic of local cohesive failures at free edges or cliffs. Specifically, a gradient of cohesion in depth seems to be necessary to observe this phenomenon. In this study, experiments with controlled cohesive grains are used to investigate the observed shape of failure, using a 3D topographic reconstruction.