Enhancing the elastoplastic damage constitutive model for clayey rocks: Incorporating anisotropy, saturation, time-dependent, and debonding effects

This paper introduced a novel microstructure-based constitutive model designed to comprehensively characterize the intricate mechanical behavior of anisotropic clay rocks under the influence of water saturation. The proposed model encompasses elastoplastic deformation, time-dependent behavior, and induced damage. A two-step homogenization process incorporates mineral compositions and porosity to determine the macroscopic elastic tensor and plastic yield criterion. The model also considers interfacial debonding between the matrix and inclusions to capture rock damage. The application of the proposed model is demonstrated through an analysis of Callovo-Oxfordian clayey rocks, specifically in the context of radioactive waste disposal in France. Model parameters are determined, followed by numerical simulations of various laboratory tests including lateral decompression tests with constant mean stress, triaxial compression tests under different water saturation conditions, and creep tests. The numerical results are compared with corresponding experimental data to assess the efficacy of the proposed model.