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

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

Chapter 5 Conclusions and Recommendations 5.1 Summary The goal of this study was to examine the relationship between the structures in the Creighton Deep and mining-induced seismicity. This was accomplished through geological investigations, seismic analysis and numerical modelling of stress. Geological investigations identified four principal systems of structures: the Footwall Shear Zone, E–W-striking shear zones, SW-striking shear zones (the 118 System) and splays between SWstriking shear zones. Numerical stress modelling demonstrates that these structures constitute weak zones within the rock mass and underground investigations indicate that such structures are healed. The Footwall Shear Zone and 1290 Shear Zone are laterally and vertically continuous but have little impact on stress or seismicity. SW-striking shear zones do not have a consistent composition and often do not correlate level-to-level. Small displacements were noted along younger fractures that cross-cut shear zones and foliation rather than along the shear zones themselves, further suggesting that shear zones are healed. Analysis of seismic events within the Creighton Deep did not reveal a relationship between structure and seismicity. Microseismic events do not spatially correspond to the mapped fault geometry. Furthermore, analysis of seismic event parameters does not reveal any spatial correlation to shear zones but does reveal areas of preferred seismic activity. Focal mechanisms of these microseismic events do not indicate any spatial correlation with structure. Consistency in focal plane solution axes for microseismic events, however, suggests that slip occurs on 106
preferentially oriented fracture planes but fracture orientations do not conform to mine-scale shear zone orientations. Macroseismic event focal mechanisms are inconsistent and fault plane solutions do not have coherent nodal planes or pressure and tension axes. A stress inversion of P- and T-axes from microseismic events on the 7400 Level indicates that mine-scale stress orientations are consistent with far-field stresses. An anomalous cluster of microseismic and macroseismic events, referred to as Cluster 1 in this thesis, exhibits unusual seismic event parameter values and stress inversion results. Influences external to the 7400 Level, including mining of the Plum Orebody and 461 Orebody, may create a complex stress environment, complicating analysis of the 7400 Level. Numerical modelling of stress on the 7400 Level shows that stress flows around the excavation, forming a ring of high stress. In this two-dimensional analysis, there is little deflection in stress trajectories in proximity to faults. This suggests that faults are strong and brittle. High stresses align parallel to SW-striking structures to the south of the excavation, lowering stresses to the southwest. Comparison of modelling results with seismicity shows an agreement between areas of high stress and areas of dense seismicity, as well as between areas of low modelled stress and areas of little to no seismicity. Numerical models that allow for non-recoverable deformation show yielding around the excavation and along SW-striking shear zones and both elastic and plastic models demonstrate slip along the Plum Shear Zone and often along the Return Air Raise Shear Zone in proximity to the excavation, though this occurs where the rockmass has yielded. 5.2 Conclusions Given that large-magnitude events require large slip surfaces, it would be expected that mine-scale shear zones would provide the area necessary to produce macroseismic events in the Creighton 107
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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
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Figure 3.7: Detected seismicity cor
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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 and 118: Figure 4.24: Fracture initiation th
Page 119 and 120: seismic Cluster 1, which correspond
Page 121: contains energetic events and is no
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
Page 169 and 170: Frequency-Magnitude Relation for Cl
Page 171 and 172: 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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