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

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$Fayek & Kyser 2000 uraninite fractionations.pdf - Queen's University$

propagation as confining stresses are relaxed. Beyond this exists a damage zone where yielding occurs with some localization along failure planes. High stresses occur on the periphery of the yield zone as the rock transitions from a fractured rock mass into a stronger, more intact rock mass. This parallels the rock mass model of an inner yield zone, damage zone and outer intact zone as discussed in Chapter 3. When the faults are weaker than the rock mass, right-lateral slip is induced on the Plum Shear Zone and often on the Return Air Raise Shear Zone to the south of the excavation. Remote to the excavation, no slip occurs along these or other discontinuities. The deflection of stress around the excavation may act to enhance the normal stress, and thus the frictional resistance, along discontinuities remote from the excavation, preventing slip. Closer to the excavation maximum principal stresses are reduced but oriented at a low angle to the Plum Shear Zone, increasing the shear stress on the fault and instigating slip in both plastic and elastic models. This, however, occurs within the yield zone and may not contribute to seismogenic slip. 4.7.1 Synthesis: Stress, Seismicity and Structure The relationship between structure and seismicity in the Creighton Deep is intimately linked to stress. The spatial distribution of seismicity closely corresponds to zones of high stress. A comparison of seismicity and stress is shown in Figure 4.25. This similar distribution supports the idea of the presence of a yield zone in proximity to the excavation where low stress and no seismicity occurs; a damage zone of high stress where dense seismicity occurs, and beyond this an intact zone where low to intermediate stress is associated with little seismicity, as discussed in Chapter 3. Both the distribution of stress and seismicity appear to be modified to align with the strike of the 118-System shear zones, but not within the shear zones themselves. The exception is 102
seismic Cluster 1, which corresponds to an area of elevated modelled differential stress but with background levels of modelled maximum stress (Fig. 4.25). Geological evidence of degradation is difficult to observe in underground conditions due to limited access and enhanced support in proximity to the excavation. However, drilling supports this degradation process. Drill cores in proximity to the main excavation (in the proposed yield zone) are heavily fractured and highly degraded (Dave Andrews; pers. comm., 2009). The damage zone has already extended below the base of the mine at the 7940 ramp, which is also evident from drilling and excavation as the mine is progressively deepened (Dave Andrews; pers. comm., 2009). Slip along mine-scale shear zones has not been identified as a failure mechanism during seismic or stress analysis. Instead, slip along existing fractures and cracking of intact rock have been demonstrated to be plausible alternative mechanisms to fault slip. Mapping zones of fracture reactivation and crack initiation using modelled stresses suggests that existing fractures without cohesion may be reactivated and new cracks can form in zones of high stress. Though modelled stresses are not elevated enough to lead to fracture interaction and coalescence, clustering of seismic events signifies the onset of yield as the rock mass is seismically weakened, which supports observations made using seismic event parameters in Chapter 2. 103
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THE INFLUENCES OF STRESS AND STRUCT
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esulting in increased stress to the
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Table of Contents Abstract.........
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4.6.1 Fracture Reactivation........
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List of Figures Figure 1.1: Locatio
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Figure 3.23: Preliminary stress inv
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Figure B11: Events between Jan 1, 2
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List of Tables Table 2.1: Geologica
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Chapter 1 Introduction 1.1 Backgrou
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Figure 1.1: Location of Sudbury and
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Chapter 2 Geological Assessment of
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ack breccia and sediments later dep
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Murray Fault, the principal fault o
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2.2 Local Geology of Creighton Mine
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B West East B’ Figure 2.4B: Longi
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Table 2.2: Fault systems within the
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Table 2.3: Summary of Fault Charact
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Figure 2.6: (A) Damage to shotcrete
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Figure 2.7: (A) The 1290 Shear Zone
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Figure 2.8: Images of (A) the 400-E
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Figure 2.9: (A) Photograph of the c
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Figure 2.10 (A) Shear foliation, in
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Figure 2.11: Thin sections of the F
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(Fig. 2.12B). Reduction of quartz g
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2.3.11 Late-Stage Fractures The you
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overprinting (Cochrane, 1991; Couls
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Table 2.4: Summary of Proterozoic t
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Both of these inferred stress direc
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are, at this time, in the process o
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Microseismic events of this subset
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3.2.1.2 Seismic Energy (E o ) and S
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3.2.1.4 Stress Parameters Stress pa
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located events were removed from cl
Page 67 and 68: Figure 3.7: Detected seismicity cor
Page 69 and 70: Table 3.1: Event characteristics in
Page 71 and 72: Table 3.3: Summary of relevant para
Page 73 and 74: ) Damage Zone The rock mass in the
Page 75 and 76: quadrants of dilatation and compres
Page 77 and 78: Figure 3.12: Lower hemisphere equal
Page 79 and 80: mechanism shows that over 57% of th
Page 81 and 82: Figure 3.16: Classification of prin
Page 83 and 84: Figure 3.18: Contoured P-axis, B-ax
Page 85 and 86: Figure 3.20: Distribution of double
Page 87 and 88: This parameter reflects the magnitu
Page 89 and 90: Figure 3.23: Preliminary stress inv
Page 91 and 92: Figure 3.25: Equal area stereonet s
Page 93 and 94: Figure 3.27: (A) Maximum principal
Page 95 and 96: 4.2 Numerical Methods Phase 2 and U
Page 97 and 98: Stress-strain relationships are use
Page 99 and 100: Rock mass failure is governed by th
Page 101 and 102: Figure 4.5: (A) Model for tectonic
Page 103 and 104: The zero cohesion and low friction
Page 105 and 106: Figure 4.9: Model of yielding for C
Page 107 and 108: Figure 4.11: Model of differential
Page 109 and 110: Figure 4.14: Model of maximum stres
Page 111 and 112: stress field model. There is little
Page 113 and 114: clustering are indications of rock
Page 115 and 116: Figure 4.23: Contoured domains of s
Page 117: Figure 4.24: Fracture initiation th
Page 121 and 122: contains energetic events and is no
Page 123 and 124: preferentially oriented fracture pl
Page 125 and 126: methodologies employed are of value
Page 127 and 128: References Alcott, J. M., Kaiser, P
Page 129 and 130: Galkin, V., Mungall, J. (2005). Str
Page 131 and 132: Mungall, J. E., & Hanley, J. J. (20
Page 133 and 134: Appendix A Geological Maps and Samp
Page 135 and 136: A.2 Level Plans with Sample Locatio
Page 137 and 138: Figure A3: 7400 Level, modified for
Page 139 and 140: Figure A5: 7680 Level, modified for
Page 141 and 142: Figure A7: 7940 Ramp, modified from
Page 143 and 144: MICROSEISMIC EVENTS Source Radius A
Page 145 and 146: 2006 Event Frequency with Depth 600
Page 147 and 148: B.2 Spatial Distribution of Seismic
Page 149 and 150: Figure B11: Events between Jan 1, 2
Page 155 and 156: Cluster 1 Source Radius Asp. Radius
Page 157 and 158: Seismic Moment 10.0 9.5 9.0 8.5 8.0
Page 159 and 160: 143 Peak Velocity Parameter -2.5 -2
Page 161 and 162: B.4.2 Temporal Distribution of Clus
Page 163 and 164: 147 Static Stress Drop 5.0 5.5 6.0
Page 165 and 166: B.4.3 Temporal Distribution of Clus
Page 167 and 168: 151 Static Stress Drop 4.0 4.5 5.0
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Frequency-Magnitude Relation for Cl
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P-axis B-axis T-axis 155 Fault Plan
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P-axis B-axis T-axis Fault Plane 1
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D.1.1: Case 1 Models Figure D1: Cas
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Figure D3: Case 1, elastic models s
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A B C D Figure D5: Case 1, plastic
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A B C D Figure D7: Case 1, plastic
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D.1.2: Case 2 Models A B C D Figure
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D.1.3: Case 3 Models A B C Figure D
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D1.4 Tectonic Loading Models Figure
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D.2 Discussion of Phase 2 Models El
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Staged models were created in which
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Figure D17 (A) Elastic model showin
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Figure D19 (A) Elastic model showin
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• Similar damage zones surroundin
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; ;================================
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change jmat=1 range 0,1564.64 0,156
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crack (845.579,718.676) (787.063,57
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;===plum=== crack (0,355.2371429) (
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crack (866.14,726.44) (838.2,737.61
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crack (838.2,737.616) (815.848,771.
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crack (815.848,771.144) (815.848,78
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;===== define sub block ===========
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E.9 S3:S1 Model for fracture reacti
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yval= abs(z_syy(zi)) xyval= abs(z_s
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and rearranged to , (Equation F4) .
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Such that , (Equation F19) I is the
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title of the thesis - Department of Geology - Queen's University

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