Automatized large-scale 3D THM simulations capturing glacial cycle effects on German nuclear waste repositories in clay rock

To properly assess the present and future conditions of potential nuclear waste repository sites, understanding their evolution in the past is mandatory. Here, glaciation cycles strongly affect the long-term thermo-hydro-mechanical (THM) evolution of the geosystem.
The AREHS project studies the effects of time-dependent boundary conditions on the evolution of large-scale hydrogeological systems. The focus is on numerical long-term modeling taking into account THM couplings. On the basis of generic geological models for different host rock formations, complex 3D THM simulations are performed. The long-term evolution during glacial cycles is simulated using the open-source multi-field finite element code OpenGeoSys, as well as multiple pre- and postprocessing tools integrated into an automatized workflow. This workflow facilitates testing/benchmarking and improves reproducibility as well as overall software quality in a sense of modularization. The impact of the glacial THM loading and atmospheric temperature evolution is taken into account using appropriate time-dependent THM boundary conditions. The simulation results are analyzed with respect to potential safety-critical parameters, such as maximum temperature, hydraulic pressure, subsidence, equivalent effective stress and strain. Some general conclusions will be drawn for the host rock clay in Germany.

Funding:

This research is funded by the Federal Office for the Safety of Nuclear Waste Management under Grant No. 4719F10402 (AREHS project).