Experimental observation of shear jamming in 3D granular materials

Frictional granular media can shear jam over a range of packing fractions below the isotropic jamming packing fraction. We experimentally study shear jamming in 3D by applying cyclic shear at fixed volume for a granular packing submerged in a density-matched solution; the effects of gravity are minimized in this environment, preventing compaction by grain weight. We observe signatures of shear jamming in the macroscopic pressure signal with a variety of packing fractions and shear amplitudes over many (on the order of 100) shear cycles. We report on analysis of particle positions (tracked via refractive index matched scanning [1]) from cycle to cycle that show correlations between microscopic rearrangements and changes in peak pressure across cycles.

[1] J. Dijksman, et. al., Review of Scientific Instruments 83, 011301 (2012)