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

Staged models were created in which the medium and discontinuities are allowed to come to
equilibrium before introducing the excavation. In this manner the stress conditions simulate
stress conditions within the mine and influence of the excavation on the distribution of stress can
be better understood. This approach did not yield appreciable differences from the applying
external stresses to a model complete with an excavation.
Unlike models created in UDEC, tectonically loaded models were not created due to limitations
on the program version.
Phase 2 results are shown for Case 1, described in Chapter 4, in which all faults are assigned equal
properties. Faults within the model are progressively weakened to induce slip by varying the
cohesion and angle of internal friction. Material properties were also tested to examine the effect
of rock mass strength on fault slip.
D.3 Phase 2 Model Results
Results for the 7200, 7400 and 7530 Level indicate that stress is bounded by faults rather than
accumulated along weaker geological structure. This indicates that seismicity is a result of the
stress concentrations that occurs between faults, rather than slip on the mine-scale structures.
The stress distribution closely matches the distribution of seismicity in the January 2006-
December 2007 time period. Areas of high maximum and differential stress are areas of dense
event localization, while areas of low modelled stress are areas of sparse activity. In plastic
models, yielding occurs directly to the north and south of the excavation and displacement is
modelled along discontinuities within this yielded zone. Low stress is modelled in this yield zone
and correspondingly, there is little-to no seismicity.
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