Shear deformation of binary mixtures of dry particulate solids

The shear deformation behavior of dry granular materials is of interest in the analysis of flowability, mixing, segregation and degradation. Quite often the particulate systems are mixtures of materials with a wide size distribution. In spite of a large amount of work reported in the literature, the shear behavior of poly-disperse systems has not been widely addressed. In this paper experimental work using an annular shear cell and numerical simulations by the distinct element method (DEM) have been carried out to quantify the normal and shear stress behavior of assemblies made of binary mixtures. The experimental results on mixtures of different sizes of glass beads show a linear relationship between the normal and shear stresses with a slope which depends on the shear rate and particle size ratio. This is an indication of flow in the intermediate regime between the quasi-static and rapid shear flows. The results also indicate a highly non-linear particle displacement distribution across the shear layer. Numerical simulations using the DEM agree qualitatively well with the experimental results for the normal-shear stress behavior.