INVESTIGATING FAULT-SLIP MECHANISMS IN SEISMICALLY ACTIVE STRUCTURES

Rock Engineering 2009 - Rock Engineering in Difficult Conditions
Nic Lightfoot, Trevor Carter,
Abstract Luiz Castro – Golder Associates
Nic Lightfoot – Golder Associates
Trevor Carter – Golder Associates
Submitted to: 3rd Canada-US Rock Mechanics Symposium & 20th Canadian Rock Mechanics Symposium

As the Canadian Mines progress to greater depth (> 2 km), the magnitudes of the induced stresses increase and are high enough to cause rock mass damage and failure during excavation. In addition, depending on the orientation of key geological structures in relation to the in situ stresses, induced shear loading can be developed on these structures, creating the potential for: a) mobilization of existing geological structures, b) formation of new seismically active structures, through rock mass damage and coalescence along a structural zone (or corridor), and c) interaction of the existing and newly created structures. Two dimensional numerical analyses were carried out to investigate four possible mechanisms that might cause fault slip on controlling structures. The four mechanisms are: (a) unclamping, (b) day-lighting, (c) stress rotation and (d) pillar shear. Application of these analyses to an underground mine in the Sudbury Basin, allowed the recommendations for two alternative methods to limit fault slip on key structures, termed: (1) pillar clamping and (2) stope sequencing.
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