Modelling weathering effects on the mechanical behaviour of granite

A conceptual model for the description of rock weathering effects is presented. The model is based on strain-hardening elastoplasticity. It is assumed that the size of the initial elastic domain of an elementary volume of rock depends on the strength of the bonds connecting the different mineral grains. Weathering reduces such strength, so that even hard rock is gradually transformed into a non- cohesive soil.In the light of the theory formulated in this paper, several weathering effects on the mechanical behaviour of granite are discussed: degradation of the shear failure loci and of tensile strength, variation of void ratio and of geo-static stresses. In particular, it is shown that for a certain degree of weathering, there exists a structural collapse of the specimen, associated to a decrease of void ratio.