Clay rocks - characterization of natural and engineered barriers

Clay rock and clay-based materials play an important role in a wide range of geotechnical and environmental applications due to their low permeability, swelling capacity, and favourable thermo–hydro–mechanical–chemical (THMC) properties. In particular, clay formations have been widely investigated as potential host rocks for the deep geological disposal of radioactive waste. In addition, clay-based materials such as bentonite are commonly used as engineered barriers in repository systems (Kolditz et al. 2024 ). Beyond radioactive waste management, clay rocks also serve as confining units for subsurface energy systems, including geological CO \(_2\) sequestration (Kühn et al. 2012 ) and hydrogen storage (Kabuth et al. 2017 ). Furthermore, clay-based materials are widely used in environmental protection systems such as landfill liners, cut-off walls, and containment barriers (Mukherjee et al. 2015 ). However, the mechanical properties of clay-rich materials often present significant challenges for engineering practice. Typically, compared to other geo-materials, clay exhibits relatively low shear strength, high compressibility, and strong sensitivity to water content. These characteristics may lead to excessive deformation, long-term settlement, and potential instability in geotechnical constructions, such as foundations, underground excavations, and slopes.