Granular jamming transition: induced by shearing and compressing*

Jamming of a granular system can be achieved by either isotropically increasing the packing fraction (isotropic jamming) or applying pure shear over a range of packing fractions below the isotropic jamming point (shear jamming). We experimentally study jammed configurations obtained by isotropic biaxial compression or pure shear in a quasi-2D granular system composed of photoelastic disks. A density matching method is applied to avoid basal friction. The fabric anisotropy and stress anisotropy are clearly different in the two cases. However, studies of the scaling behavior near the jamming transition reveal that, as the transition is approached, the scaling exponent of the pressure is the same for the isotropic jamming and shear jamming cases.