Micromechanic Formulation of Macroscopic Structures in a Granular Medium

A granular medium is viewed as a heterogeneous continuum that satisfies mechanical equilibrium at each material point. Analysis of the strain distribution under deviatoric loading displays structures formation when the strain pattern is filtered through a directionally sensitive deformation intensity analyzer. The same type of analysis carried out on numerical experiments yields similar structures. Comparison between the two methods permits an estimate of the radius of the mesodomain that is characteristic for granular media. This scale is one of the necessary scales of discrimination that is needed for the understanding of the deformation of granular materials with elastofrictional particle interaction. Evolution of the thickness of the structures is also analyzed. They become elongated with increasing deviatoric deformation. The encroachment of the mesoscale onto the microscale (that is, the particle interactive scale) is signaled.