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

weak fault condition represents a reasonable failure band fault strength used to examine the effect
of very weak faults.
Both elastic and plastic models are tested under these conditions. For all fault conditions, the
model is subjected to a compressive stress field where σ 1 = –102.7 MPa and σ 3 = –73.4 MPa.
Stress magnitudes are based on stress estimates for the 7400 Level, derived from overcoring stress
measurements made by Creighton Mine. The negative sign convention in UDEC indicates
compressive stress.
Table 4.2: Fault parameters tested for Case 1.
Fault Condition
Cohesion Friction
(MPa) Angle (º)
Locked 50 50
Strong 5 35
Moderately Strong 0 35
Weak 0 20
Both elastic and plastic models for maximum stress, differential stress, slip, and yielding produce
similar results. The locked fault condition produces low maximum and differential stresses
immediately to the north and south of the excavation. Further from the excavation, high stresses
form a ring around the excavation. As the cohesion is lowered at a constant friction angle, from
the strong to the moderately strong model, maximum stress (Fig. 4.6) and differential stress (Fig.
4.7) is enhanced to the south and southeast of the excavation and diminished to the southwest of
the excavation. When the friction angle is very low (the weak fault case), stress is diminished to
the south of the excavation and high stresses are pushed farther outwards away from the
excavation. Yielding in the plastic models aligns with the strike of the 118 System shear zones
and further slip is induced along shear zones in proximity to the excavation.
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