Rigidity percolation and stick-slip dynamics in sheared granular material

Granular materials are inherently heterogeneous and their bulk behavior is tied to interactions between constituent particles. Predicting rigidity and failure, which is of particular importance in geophysical and engineering applications, is notoriously difficult. One method to predict rigidity is by using constraint counting to identify networks of self supporting rigid clusters. Once the rigid clusters grow to be system-spanning the material is said to be rigid. The transition between rigidity and failure is not well understood when a material is loaded by increasing stress. Here, we use a photoelastic granular system in an annular shear cell to study the correlation between large scale slip events (failure) and rigid clusters. In these experiments, we apply a constant stress rate until a slip event and record particle positions and vector contact forces as well as torque measurements from the driving motor and rotation of the annulus. We use the pebble game algorithm to identify rigid clusters and connect their mesoscale dynamics to the bulk stick-slip behavior.