Résumé
Granular media represent a remarkable example of materials endowed with a discrete structure in which steric exclusions and topological disorder (grain connectivity through a network of intergrain contacts) are fundamental for rheology. We propose a general framework for investigating this link between microstructure and plastic behavior in the case of a granular material composed of rigid grains at quasistatic equilibrium. We discuss the nature of microstructural variables and we show that setric exclusions and the equilibrium condition lead to a domain of accessible states in the phase space. The results are compared to numerical simulations.