Short Course 3

Level: Foundation

Structural geology and geomechanics play a central role in the safe and sustainable management of nuclear waste, particularly where long-term mechanical stability and geological integrity must be ensured over timescales of thousands to millions of years. This course on Structural Geology and Geomechanics in Nuclear Waste Management provides a comprehensive understanding of how geological structures, stress regimes, and failure mechanisms influence the selection, design, and monitoring of nuclear waste repositories. With a strong emphasis on mechanical failure criteria – especially the Mohr–Coulomb failure model – the course links fundamental geological theory with applied engineering and regulatory practice.

The course begins by outlining the broader context of nuclear waste management and the rationale for geological disposal as the preferred long-term solution for high-level and long-lived radioactive waste. Key repository principles such as isolation, containment, and the use of engineered and natural barriers are introduced. Within this framework, structural geology is presented as a critical discipline, as faults, fractures, folds, and other deformation features directly influence rock strength, permeability, and long-term stability. Understanding these features is essential for evaluating whether a geological formation can safely host a repository without compromising containment or increasing the risk of contaminant migration.Part of the course is dedicated to the principles of structural geology, with particular attention to the identification, mapping, and interpretation of geological structures in the subsurface. Geological structures are treated as dynamic elements whose evolution must be considered in long-term safety assessments, particularly in response to natural stresses, repository excavation, and thermally induced stresses resulting from radioactive decay.
Central to the course is the application of failure criteria, with the Mohr–Coulomb model serving as the primary analytical framework. The theoretical basis of this model is explored, including concepts of normal and shear stress, cohesion, internal friction, and stress envelopes. Practical examples and case studies demonstrate how laboratory-derived strength parameters are transferred to field-scale assessments and how uncertainties in material properties affect safety margins.
Building on this foundation, the course addresses site stability assessment and the determination of mechanical strength parameters in repository design. Particular emphasis is placed on the role of faults and fracture networks as zones of weakness or potential fluid pathways, and on the interaction between geological structures and engineered components such as tunnels, shafts, and waste canisters.
Monitoring and long-term observation form another key theme. Methods for detecting subsurface deformation, stress redistribution, and damage evolution – such as geodetic measurements and microseismic monitoring – are presented as essential tools for safety assessment, adaptive management, and regulatory compliance.
Consequently, the course situates structural geological and geomechanical analysis within broader risk assessment and regulatory frameworks, demonstrating how structural geological data and failure criteria support safety cases and long-term decision-making in nuclear waste disposal.