The excavation damaged zone in clay formations – time-dependent behaviour and influence on performance assessment

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Abstract

Clay formations in their natural state exhibit very favourable conditions for disposal of radioactive waste. One concern regarding waste disposal is that due to the necessary underground excavations and the associated disturbance and damage in the area close to these excavations, the favourable properties of such formations could change and the host rock could lose part of its barrier function. Stress redistribution will lead to the creation of a so-called excavation damaged zone (EDZ) which will be controlled by the initial stress field, the material properties (e.g., material anisotropy), the existence of natural fracture zones or local inhomogeneities of the rock mass and the geometry of the tunnel. Comprehensive investigations at different sites (e.g., HADES, Belgium, Mont Terri, Switzerland, Tournemire, France) have shown that an EDZ occurs in soft or plastic clays as well as in indurated and more brittle claystones. Performance assessment calculations for different repository designs in different clay host rock formations show that the influence of the EDZ on radionuclide release is quite limited. It has been shown that even for very conservative, so-called ‘‘what if?’’ cases the very stringent regulatory guidelines can be met.

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Original languageEnglish
Pages (from-to)588-599
JournalPhysics and Chemistry of the Earth
Volume32
Issue number8-14
DOIs
Publication statusPublished - Feb 2007
EventClays in Natural & Engineered Barriers for Radioactive Waste Confinement - ANDRA, Tours, France
Duration: 14 Mar 200518 Mar 2005

Keywords

  • Excavation disturbed zone, radionuclide transport, performance assessment, hydraulic conductivity

ID: 309753