In a repository of high-level radioactive waste, long-term complex thermal, hydraulic and mechanical (THM) phenomena will take place, involving heat generation from the waste, infiltration of ground water and swelling of bentonite buffer. The capability of modeling such coupled phenomena is of particular importance to the repository design and the safety assessment. The authors have developed an in-house THM coupled analysis code for evaluating the long-term behavior around the repository (called "near-field"). The authors have also conducted centrifugal model tests that model the long-term THM coupled behavior in the near-field.
In this paper, HM coupled and THM coupled numerical simulations of the centrifugal near-field model tests were conducted. Numerical results were compared to each other and to the results from the centrifugal model tests mainly of the constant temperature condition. Following remarks were obtained from the comparison:
Water infiltration in rock mass in the numerical simulation agreed with the experimental observation,
Constant stress boundary condition in the centrifugal model tests may cause larger expansion of rock mass than in in-situ condition but the mechanical boundary condition did not affect the buffer behavior in the deposition hole,
The numerical simulation broadly reproduced the measured bentonite pressure and the overpac displacement but did not reproduce the decreasing trend of the bentonite pressure after 100 equivalent years. This fact indicates the effect of time-dependent characteristics of a surrounding rock mass.
Water infiltration in the temperature gradient condition was different from that in the constant temperature condition because of temperature dependency of water viscosity and heat-induced vapor diffusion near the overpack.
The further investigation is needed for the effect of initial heterogeneity in the depsition hole and the time-dependent behavior of the surrounding rock mass.
