Unsteady Shear of Dense Assemblies of Cohesive Granular Materials under Constant Volume Conditions

The response characteristics of dense assemblies of cohesive granular materials to unsteady simple shear in the quasi-static regime are investigated through discrete element method (DEM) simulations of monodisperse spherical and frictional particles in periodic domains at constant volume. The dynamics of the volume-averaged normal and shear stresses in materials, undergoing stop-and-go shearing and oscillatory shear, are studied in detail. Furthermore, the evolution of microstructure anisotropy has been quantified through a fabric tensor. The stresses and the microstructure anisotropy depend on the strain extent but not on the shear rate. They both undergo a transition following reversal of shear direction, which requires a shear strain of order unity to fully adapt. The results reveal a correlation between the stress evolution and the microstructure anisotropy development.