Clay rocks—characterization of natural and engineered barriers

Clay rocks and clay-rich materials play an important role in numerous geotechnical applications.Due to their thermal hydraulic, mechanical and geochemical properties, clay rocks are suitable as a natural barrier, and thus are of great interest as host rocks for the deep geological disposal of radioactive waste.There are already corresponding site proposals in France and Switzerland, for example.Various Opalinus Clay, Callovo-Oxfordian and Rupelton clays are being intensively investigated in underground research laboratories such as Mont Terri (Switzerland) (Bossart et al. 2017; Nussbaum et al. 2023), Bure and Tournemire (France) Yuan et al. (2023) and Mol (Belgium) (Honty et al. 2022).Clay rocks furthermore play an important role as confining units for georeservoirs, e.g. for the geological storage of CO 2 (Khn et al. 2012) and H 2 (Kabuth et al. 2017).According to the conceptual design of a multi-barrier repository for radioactive waste, clay-based materials such as bentonite also serve as an important engineered barriers for repository tunnels and shafts: they help maintain the structural stability of the repository and the canisters,