Memory of biaxial compression during shear jamming in granular materials

We have designed a novel experimental apparatus to probe the jamming features of granular materials based on photoelastic techniques. The experiment consists of a floating layer of photoelastic disks, which is subject to deformation (compression or shearing). We first compress the granular sample to detect the jamming packing fraction of a given systemusing the photoelastic response. This also yields the force chain networks and stresses throughout the material. we decompress the system to a certain distance from the jamming point.We next decompress the system below jamming, and then apply pure shear, lead to a shear jammed state. We compare the force network, coordination number and local density distribution for the states obtained by compression vs. those obtained by shear jamming state when the systems have the same pressure to understand structural similarities in the two types of states.