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Environmental Geology

, Volume 57, Issue 6, pp 1371–1389 | Cite as

Implications of subsurface thermal–hydraulic–mechanical processes associated with glaciation on Shield flow system evolution and performance assessment

  • Tin Chan
  • Frank W. Stanchell
Special Issue

Abstract

A deep geologic repository (DGR) situated on the Canadian Shield will be subject to long-term climate change that will markedly alter surface conditions as a result of glaciation and permafrost penetration. Systematic, two-dimensional and three-dimensional coupled thermal–hydraulic–mechanical finite-element simulations with varying degrees of coupling, including depth-dependent salinity (represented as a change in groundwater density) and temperature-dependent density and viscosity, were undertaken to address the implications of glaciation on groundwater flow system dynamics as it could affect DGR performance. The modelling domain consisted of a 1.6-km deep sub-regional scale (≈100 km2) fractured Shield flow system. Initial and transient thermal, hydraulic and mechanical boundary conditions were developed from two realizations of the University of Toronto Glacial Systems Model of the last Laurentide glaciation. Results indicate that during the glacial loading/unloading cycle, for this particular conceptual model, there is limited penetration of glacial meltwaters to depth and small residual anomalous hydraulic head. During glacial coverage, the mechanical factor of safety increases in the moderately fractured and sparsely fractured rock mass, but principal effective stress reorientation also occurs. Given the assumed nonglacial in situ state of stress and mechanical properties, the fracture zones were predicted to be less stable under glacial conditions.

Keywords

Canadian Shield Glaciation Thermal–hydraulic–mechanical (THM) modelling Glacial meltwater infiltration Anomalous head 

Notes

Acknowledgments

This study was funded by the Nuclear Waste Management Organization (NWMO) as part of its technical research and development program. The authors thank Andre Vorauer, Mark Jensen and Ben Belfadhel of NWMO for project guidance, technical discussions and/or technical reviews, Prof. W. R. Peltier for providing detailed results of University of Toronto glaciation model, L. Cotesta and P. K. Kaiser of MIRARCO Mining Innovation for scientific visualization support and in situ stress recommendation, respectively, S. D. Normani for providing electronic files of the DEM, surface water hydrology and boundary coordinates, T. S. Nguyen of the Canadian Nuclear Safety Commission for valuable suggestions, an anonymous reviewer for careful perusal and editorial corrections of the manuscript and Bonnie St. Denis for expert word-processing. This paper does not necessarily reflect the views or positions of NWMO. The authors are solely responsible for all contents and views in this paper.

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Copyright information

© AECL 2008

Authors and Affiliations

  1. 1.Station 37, Whiteshell LaboratoriesAtomic Energy of Canada Limited (AECL)PinawaCanada
  2. 2.Formerly of AECLWinnipegCanada

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