Characterization of the long-term hydro-mechanical response in the host rock of a potential nuclear waste disposal repository

Clayey rock, in virtue of its properties, such as low permeability, self-sealing, etc., is considered to be a candidate host rock for underground nuclear disposal facilities. In this paper, we take clayey rock as our study object. Analyzing the related test results of clayey rock both in the laboratory and in situ, a nonlinear creep damage constitutive model has been established. This theoretical model considers the creep damage, as well as the creep strain accumulation effect. Based on the software of ABAQUS, we compiled the corresponding UMAT subroutine. A numerical analysis of the long-term hydro-mechanical response of a nuclear underground repository was carried out. The results indicate that: (1) the nonlinear creep constitutive model can well show the creep process of clayey rock. (2) The deformation, as well as the pore water pressure of the host rock, are significant influenced by the tunnel excavation. The pore water pressure soon decreases with deformation increases after the tunnel excavation. (3) The deformation of the host rock is closely related to the excavation distance and creep time. The excavation effect for both deformation and pore water pressure weakens as the increase of distance between the target location and the excavated tunnel. Meanwhile, due to the time effect, the pore water pressure, as well as the deformation around the tunnel gradually increased. (4) The consensus of the numerical simulation and in situ measurements on the deformation of tunnel linings show the reliability of the theoretical model. The research here will give significant guidance on the long-term stability analysis of the clayey rock nuclear waste repository in China. © 2022, Science Press. All right reserved.