Popping: A granular transition

In experiments conducted on a weakly confined 2D assembly of deformable cylinders subject ed to rapid in-plane shear loading, we have identified the key obstacle in achieving compaction. This obstacle involves a dynamic transition between mechanical instabilities, progressing from in-plane rearrangement to out-of-plane popping as the density increases. The popping effect reinforces the frictional constraints from the confining wall and restricts particle mobility, impeding the system from attaining greater compaction. We quantify this transition and demonstrate that interparticle friction contributes to smoothing the transition.