Geomaterials, such as soils and rocks, have a clearly defined microstructure at the level of individual grains. The study of the mechanical behaviour of geomaterials, especially at or after failure, therefore focuses on their micromechanics, i.e. on the relation of the overall material behaviour to the interaction between adjacent grains. To properly model the post-failure behaviour (e.g. strain localisation) within the framework of continuum mechanics, it is usually necessary to resort to a generalised continuum formulation, such as Cosserat or strain-gradient models. This presentation will provide an overview of the use of generalised continuum models to describe micromechanical effects in geomaterials. Questions related to constitutive modelling and the choice of specific generalised formulations and related plasticity models will be discussed, as well as issues concerning the numerical implementation of these models. Finally, recent developments and current research directions will be presented.
