Rapid granular shear flows show complex behaviors so that they can be assumed as fluids solely or as mixtures of fluids and solids. We have performed experiments on annular granular shear flows using monodisperse and bidisperse steel spheres with 2 and 3 mm in diameter. We present some time-dependent (failure of material due to shear) and steady state (completely- and partially-sheared flows) features of rapid granular flows of these samples. Our results map out the boundary between overall compaction and dilation that characterizes multiphase behavior of system. Dimensionless stresses rise as more material is loaded into the system. On the other hand, increasing compressive force or shear rate facilitates the process of shearing by decreasing the ratio of shear to normal stress.

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