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

fractured and behaves as a rock mass under pre-peak conditions. Similarly, the rock mass in the
Creighton Deep can be divided into three zones based on the characteristics of seismicity (Fig.
3.9):
Figure 3.9: Sketch depicting location
of (A) Yield Zone, (B) Damage Zone
and (C) Intact Zone. Major principal
stress is oriented East-West
a) Yield Zone
The yield zone occurs adjacent to the excavation to the north and south. It is the result of damage
directly incurred by mining. Here the rock mass has undergone seismic softening (sustained
degradation through seismic activity) and is heavily fractured. Progressive damage has resulted in
permanent strain, low stress and has rendered this zone aseismic. The shape of the damage zone
reflects both the shape of the excavation and the stress tensor, in which the maximum principal
stress is near-horizontal and oriented east-west.
Little to no seismicity occurs immediately north or south of the excavation. The rock mass in this
area is less confined and is expected to have been degraded by mining activity, classifying it as the
Yield Zone. Gravity-driven failure (fall of ground) occurs in this region and results from seismic
shaking (Vale Inco, pers. comm., 2009).
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