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

Damage zones produced using maximum stress and differential stress outline similar areas of
fracture initiation. Areas of active excavation during the 2006-2007 time period as well as a zone
of high-stress between the Return Air Raise Shear Zone and Plum Shear Zone are identified as
areas of possible fracture initiation under both maximum stress and differential conditions. This
demonstrates that fracturing of intact rock is a possible mechanism for seismicity to the south of
the excavation where seismicity is observed, but the crack coalescence threshold is not surpassed.
Fracture contours identify the area south of the excavation as a region that is in a state of damage
but not yield (Fig. 4.24). This is a lower state of degradation than was found in Chapter 3 using
seismic source parameters, where the rock mass to the south of the excavation was hypothesized
to be in post-peak conditions.
Figure 4.24 shows that cracking is not possible immediately to the north and south of the
excavation, based on the final state of models produced for Case 1 (Φ=30 o , C=0 MPa). This is
because yielding has already occurred and high stress cannot be accommodated by the
disintegrated rock mass in this state. UDEC code and routines can be found in Appendix E.
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