A pragmatic approach to abstract the excavation damaged zone around tunnels of a geological radioactive waste repository: application to the HG-A experiment in Mont Terri
Andrés Alcolea, Uli Kuhlmann, Paul Marschall, Andrea Lisjak, Giovanni Grasselli, Omid Mahabadi, Rémi de La Vaissière, Helen Leung, Hua Shao, 2017. "A pragmatic approach to abstract the excavation damaged zone around tunnels of a geological radioactive waste repository: application to the HG-A experiment in Mont Terri", Radioactive Waste Confinement: Clays in Natural and Engineered Barriers, S. Norris, J. Bruno, M. van Geet, E. Verhoef
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The excavation damaged zone (EDZ) around the backfilled tunnels of a geological repository represents a possible release path for radionuclides, corrosion and degradation gases that needs to be adequately addressed by safety assessment (SA) modelling tools. The hydromechanical phenomena associated with the creation and temporal evolution of the EDZ are of high complexity, precluding detailed representations of the EDZ in conventional SA. Thus, simplified EDZ models mimicking the safety-relevant features of the EDZ are required. In this context, a heuristic modelling approach has been developed to represent the creation and evolution of the EDZ in an abstracted and simplified manner. The key features addressed are the stochastic character of the excavation-induced fracture network and the self-sealing processes associated with the re-saturation after backfilling of the tunnels. The approach has been applied to a range of generic repository settings to investigate the impact of repository depth and in situ conditions on the hydraulic significance of the EDZ after repository closure. The model has been benchmarked with a dataset from a self-sealing experiment at the Mont Terri underground rock laboratory (URL), demonstrating the ability of the approach to mimic the evolution of the hydraulic significance of the EDZ during the re-saturation phase.
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It is internationally accepted that the safest and most sustainable option for managing radioactive waste is geological disposal, utilizing both engineering and geology to isolate the waste and contain the radioactivity.
This Special Publication contains 25 scientific studies presented at the 6th conference on ‘Clays in natural and engineered barriers for radioactive waste confinement’ held in Brussels, Belgium in 2015. The conference and this resulting volume cover many of the aspects of clay characterization and behaviour considered at various temporal and spatial scales relevant to the confinement of radionuclides in clay, from basic phenomenological process descriptions to the global understanding of performance and safety at repository and geological scales.
The papers in this volume consider research into argillaceous media under the following topic areas: large-scale geological characterization; general strategy for clay-based disposal systems; geomechanics; mass transfer; bentonite evolution and gas transfer.
The collection of different topics presented in this Special Publication demonstrates the diversity of geological repository research.