A constitutive model for anisotropic clay-rich rocks considering micro-structural composition

A new constitutive model is developed in this paper for clay-rich rocks. This model describes elastic, instantaneous and time-dependent plastic deformations, and induced damage. The dependency of mechanical behavior of clayey rocks on water saturation degree is taken into account. Further, the structural anisotropy commonly exhibited by sedimentary rocks is also incorporated in the proposed model. Moreover, differently with most full phenomenological models, the impact of micro-structural composition on the macroscopic mechanical behavior is explicitly described by the presented model. More precisely, the macroscopic elastic properties and plastic criterion are determined by using analytical homogenization techniques. These properties explicitly depend on mineralogical compositions and porosity. The damage process is physically related to the interface debonding between clay matrix and mineral particles. The proposed model is applied to the Callovo-Oxfordian claystone investigated in the context of geological disposal of radioactive waste in France. Its efficiency is assessed through comparisons between numerical predictions and experimental data from laboratory tests under different loading paths and water saturation degrees.