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We study the jamming phase diagram of sheared granular material using a novel Couette shear set-up with multi-ring bottom. The set-up uses small basal friction forces to apply a volume-conserving linear shear with no shear band to a granular system composed of frictional photoelastic discs. The set-up can generate arbitrarily large shear strain due to its circular geometry, and the shear direction can be reversed, allowing us to measure a feature that distinguishes shear-jammed from fragile states. We report systematic measurements of the stress, strain and contact network structure at phase boundaries that have been difficult to access by traditional experimental techniques, including the yield stress curve and the jamming curve close to $phi_{SJ}approx 0.74$, the smallest packing fraction supporting a shear-jammed state. We observe fragile states created under large shear strain over a range of $phi < phi_{SJ}$. We also find a transition in the character of the quasi-static steady flow centered around $phi_{SJ}$ on the yield curve as a function of packing fraction. Near $phi_{SJ}$, the average contact number, fabric anisotropy, and non-rattler fraction all show a change of slope. Above $phi_{F}approx 0.7$ the steady flow shows measurable deviations from the basal linear shear profile, and above $phi_capprox 0.78$ the flow is localized in a shear band.
We report on experiments that probe the stability of a two-dimensional jammed granular system formed by imposing a quasistatic simple shear strain $gamma_{rm I}$ on an initially stress free packing. We subject the shear jammed system to quasistatic c
We present experiments on slow shear flow in a split-bottom linear shear cell, filled with layered granular materials. Shearing through two different materials separated by a flat material boundary is shown to give narrow shear zones, which refract a
Jammed systems all have a yield stress. Among these materials some have been shown to shear-band but it is as yet unclear why some materials develop shear-band and some others do not. In order to rationalize existing data concerning the flow characte
The mechanical and transport properties of jammed materials originate from an underlying per- colating network of contact forces between the grains. Using extensive simulations we investigate the force-percolation transition of this network, where tw
Nonequilibrium steady states of vibrated inelastic frictionless spheres are investigated in quasi-two-dimensional confinement via molecular dynamics simulations. The phase diagram in the density-amplitude plane exhibits a fluidlike disordered and an