A Continuum Modelling Study of Macro-Geometry choices and Their Impact on Excavation Damage Zone Development in Brittle Rock at Depth
Canadian and International experts agree that deep underground repositories are the single best solution regarding safe, long-term nuclear waste disposal (IAEA 2009). Numerous European and Asian countries have already begun extensive research and preliminary design analyses associated with site assessment for high-level fuel storage facilities known collectively as deep geological repositories (DGRs) (ANDRA 2005, Armand et al. 2003, NAGRA 2002, Martino and Chandler 2004). In Canada, Kincardine, ON, is currently the proposed site that will host the low- to medium-level nuclear waste generated from the Bruce, Pickering and Darlington nuclear power plants. The project conceptualization, as well as the specific sites, have undergone extensive public critique and analyses. The project is in the final licensing stage of the process. To ensure long term stability and safety of the DGRs, the prediction and understanding of the excavation damage zone (EDZ) around the associated shafts, placement room tunnels, storage voids and access tunnels is paramount. The general EDZ consists of component zones of damaged, fractured and influenced rock moving radially away from the center of the excavation. The outer “influenced” zone consists of rock that has been elastically strained, while the “damaged” zone undergoes small scale, discontinuous crack damage, subsequently increasing the permeability of the surrounding rockmass. The “fractured” zone is located nearest to the excavation wall/face, where continuous (connected) fractures dominate. Numerous details within a preliminary design of the tunnels and intersections within a DGR will influence the development and ultimate impact of the EDZ on ultra-long-term repository safety. For the various DGR tunnelling projects that include the placement room tunnels, access tunnels and vertical shafts, details of shape will dictate the ultimate support demands and safety requirements. Using case examples, as well as 2-dimensional and 3-dimensional continuum numerical modelling simulations, this thesis will illustrate key impacts of macro-geometry choices, such as shape and dimensions of placement room and access tunnels, as well as details, which include corner geometry, aspect ratio, excavation sequence and methodology, on EDZ and highly damaged zone (HDZ) development in underground infrastructure.
URI for this recordhttp://hdl.handle.net/1974/22772
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