Modelling of inherent anisotropy in sedimentary rocks

This paper presents a constitutive relation for modelling the inelastic response of sedimentary rocks. The inherent anisotropy of this class of materials is described by employing a second-order microstructure tensor, whose eigenvectors define the principal material triad. Higher-order dyadic products of this tensor are incorporated in the distribution function, which specifies the directional dependence of strength parameters. The mathematical formulation is applied to model the mechanical characteristics of Tournemire shale. Several triaxial tests are simulated, at various initial confining pressures, for samples tested at different orientation relative to the loading direction. The results are compared with the available experimental data