This presentation discusses a series of in situ experiments of fault activation by fluid injection conducted in argillite rock at the Mont Terri underground research laboratory in Switzerland to better understand whether pressurization of natural faults can lead to their reactivation and permeability generation in case such features are present near disposal tunnels. Lessons learned from these experiments help inform the safety assessment of geologic disposal in argillite host rock.

More than a decade ago, the US Department of Energy (DOE) initiated a new research and development (R&D) program to provide a sound technical basis for geologic disposal options across clay, crystalline, and salt host rocks. The program established partnerships with international institutions and developed a number of collaborative R&D activities. This presentation gives an overview of these activities, with a focus on the coupled processes occurring in engineered and natural barriers.

Bentonite buffer surrounding the waste canister is a critical part of the multi-barrier system for high-level radioactive waste geological repositories that undergo heating from heat-emitting waste and hydration from the host rock. Thus, extensive research was conducted to study the alteration of bentonite due to heating and hydration under high temperatures (200 °C); this work provides valuable data for model validation.

This presentation gives an overview of an international research collaboration for advancing the understanding and modeling of coupled thermo-hydro-mechanical-chemical (THMC) processes in geological systems. DECOVALEX emphasizes joint analysis and comparative modeling of state-of-the-art field and laboratory experiments, across a range of host rock options and repository designs.