Invariants of stress and fabric tensors in charged granular systems subjected to shearing

Using computer simulations, we studied the micromechanical characteristics of charged granular media (cohesive and frictional sphere assemblies) subjected to quasi-static shearing. Contrary to the normal expectation, our analysis show that the macroscopic octahedral shear stress tensor in charged granular systems which is associated with distortional changes during shearing originates from the anisotropic orientation of a small proportion of (heavily loaded) contacts. Electrostatic force between the grains enhances geometric stability of the charged granular media during slow shearing. Although charging influences the octahedral stress and fabric measures at both the microscopic and macroscopic scales, their effect is relatively more dominant in low-frictional systems. The key results presented here on the micromechanical shear deformation properties of discrete materials could form as a basis, as well as complement other methods, in describing the constitutive behaviour of charged granular media.