Probing the Hydro-mechanical Response of a Clayey Rock for Radioactive Waste Disposal Using a Transversely Isotropic Damage Constitutive Model

To develop a geological nuclear waste disposal facility from scratch, the hydro-mechanical properties of the host rock are fundamental for its initial construction, long-term system evolution, closure, and post-closure phases. In this paper, a transversely isotropic damage constitutive model was developed to describe the nonlinear behavior of clayey rock, based on the modified Drucker–Prager Cap model. Considering the self-sealing effect, a hydraulic conductivity evolution law of typical clayey rock was established based on in situ measurements. These theoretical models were further implemented in the finite element method software ABAQUS FEA (Finite Element Analysis) utilizing the subroutine USDFLD, which is a user subroutine to redefine field variables at a material point in ABAQUS. The hydro-mechanical response of an underground research laboratory during excavation and operation was reproduced by three-dimensional numerical simulation to validate the proposed models. The results highlighted that the developed theoretical model could efficiently reproduce the evolution of pore water pressure and deformation, compared to the in situ measurements in the excavation damaged/disturbed zone (EDZ) and hydraulic disturbed zone (HDZ) driven by tunnel excavation.