title of the thesis - Department of Geology - Queen's University

A
B
Figure 4.3: (A) Complete model geometry; (B) excavation and fault geometry within inner box in (A) is
shown with labeled discontinuities and excavation. The area outside the inner box in (A) is subject to
boundary effects. SZ = shear zone.
The excavation on the 7400 Level consists of backfilled and unfilled stopes and sills. These are
modelled as one large void. This can be done under the assumption that backfill has little loadbearing
capacity and stiffness compared to the surrounding rock mass and thus can be ignored in
the models. Drifts and small excavations remote from the main excavation have been omitted to
simplify the level model, as they have negligible effect on the mine-scale stress field.
Strength parameters for the medium surrounding the excavation reflect rock mass quantities rather
than laboratory values for intact rock, which overestimate strength (Pande et al., 1990; Schultz,
1996). These rock mass parameters (summarized in Table 4.1), except where noted, were taken or
calculated from estimates made by Coulson (1996) for footwall rocks in Creighton Mine. Values
for normal and shear stiffness have been increased from calculated values to prevent contact
overlap. The boundaries of the model, and thus the medium, are created far from the excavation.
This ensures that modelled stress around the excavation is free from edge effects that result from
the modelling process.
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