Influence of a non-random fabric on macroscopic properties of geomaterials

This paper is concerned with the mathematical description of the deformation process in geomaterials. In particular, the response as observed on the macroscale is correlated with some implicit measures of the material microstructure. First, a plasticity formulation is reviewed which attributes the anisotropy in mechanical behaviour to a bias in the spatial distribution of voids. Subsequently, the case of a spontaneous loss of material homogeneity, resulting from formation of a shear band, is addressed. A new mathematical formulation for the description of localized deformation is derived, based on considering the material as a two-phase composite. The resulting homogenized constitutive relation can represent the unstable material response, i.e. strain softening.