A micromechanics-based methodology for evaluating the fabric of granular material

A micromechanics approach can successfully model the stress-strain-strength relation of a granular material once the microcharacteristics of the mater ial have been obtained. However, it is usually difficult to determine the f abric of natural granular materials, Using a stress-dependent micromechanic s model, the elastic properties can become a function of the geometric and kinetic fabric. Also, the wave velocity can be related to the elastic prope rties, Consequently, this paper proposes a methodology for evaluating the f abric of a granular assembly from a set of measured wave velocities. The me thodology contains three elements: (a) stress-dependent micromechanics elas tic model, (b) an anisotropic elastic wave propagation theory and (c) an op timization procedure. It is verified by calibrating available wave velocity data of a glass bail assembly and washed mortar sand, The methodology is f urther applied to study the microstructural evolution of the washed mortar sand under biaxial stresses. Two aspects of fabric change can be observed: (a) concentration of contact normals in the major principal direction and ( b) a residual fabric after subsequent loading/unloading.