Gravity and friction in shear jamming of 3D granular materials

Shear jamming occurs in 2D frictional particles over a range of packing fractions below isotropic jamming. Simulations show shear jamming for frictionless spheres, but over a vanishing range as the system size grows. We use packings of submerged hydrogel particles to determine the shear-induced macroscopic response of 3D, low-frictional granular systems near jamming, bridging the gap between frictionless and low-frictional packings. We find that a ~0.4% density-mismatch easily compacts the low frictional (μ ~ 0.03) system, superseding shear jamming and highlighting the importance of gravity. We perform experiments with density-matched high- and low-frictional particles to recover a macroscopic shear jamming response in 3D and elucidate the role of friction in shear jamming. Accompanying DEM simulations corroborate our experimental results.