Jamming by shear in a dilating granular system

Abstract

Jamming can occur in frictional granular materials undergoing shear at a fixed packing fraction, $$\phi $$, within a range below the isotropic jamming point, with the amount of strain required to induce jamming, $$\gamma $$, increasing with decreasing $$\phi $$. We are interested in how the shear jamming process is affected when the system dilates as it is sheared. We conduct experiments to shear a 2D granular system while continuously increasing the system volume. Below a certain dilation rate, the system is still able to jam for $$\phi $$ smaller than the initial $$\phi _0$$. We measure $$\gamma $$ for different dilation rates and initial packing fractions by monitoring the coordination number of non-rattlers and the system pressure. We find that $$\gamma $$ is the same as the $$\gamma $$ required to jam a system with fixed packing fraction $$\phi $$ via pure shear.