A non-uniform transformation field analysis for frictional cohesive geomaterials

This paper is devoted to the micromechanical analysis of effective behavior of heterogeneous materials with pressure-dependent plastic constituents. The micromechanical model is based on an extension of the NTFA method proposed by Michel and Suquet (2003, 2004). The local plastic strain field is divided into a volumetric part and a deviatoric part. Each part is expressed as a linear combination of relevant non-uniform plastic strain fields, called “plastic modes”. The non-uniform microscopic strain fields are thus described by a finite number of reduced internal variables. And the local constitutive models are then reformulated in terms of such variables. The proposed model is applied to two typical heterogeneous materials: inclusion reinforced composite and porous material. Numerical results obtained by the NTFA are compared with the direct finite element solutions. In particular, the macroscopic yield stresses of porous materials are compared between the NTFA and some recently proposed analytical criteria. Finally, as an application example, the micromechanical model is used to simulate laboratory tests performed on porous sandstone.