ABSTRACT
The stress-strain behaviour of geomaterials is frequently modelled using elasto-plastic constitutive models. The design of elasto-plastic constitutive models involves a comprehensive description of a series of stress surfaces classifiable as plastic potential, yield surface and failure surface. This paper presents a generic stress surface formulated in terms of principal stresses, that can operate as such stress surfaces in an elasto-plastic constitutive model. As the shape of these stress surfaces is quite different with respect to the mean effective stress the proposed stress surface is established for constant values of the mean effective stress. The generic stress surface has been developed on the basis of the Customised Octahedral plane, which is introduced prior to the description of the generic stress surface. The formulation is initially established for an isotropic material but the paper also demonstrates how it can be extended to the case of cross-anisotropic behaviour.
