Large-magnitude seismicity at the Westwood mine, Quebec, Canada

Abstract

The Westwood mine is located approximately 40 km east of the town of Rouyn-Noranda and 80 km west of the town of Val-d'Or in Quebec, Canada. Operations at the Westwood mine were halted by three large-magnitude seismic events which occurred over two days in May, 2015. This paper provides an overview of the seismic events and summarises the numerical back-analyses completed using global mine-scale and local drift-scale models, to gain an understanding of the mechanisms that fundamentally contributed to what was considered, by a review panel of experts, to be an unforeseen series of events. A global mine model was required to provide a reasonable estimate of the induced stresses on nearfield pillars and excavations and a detailed small-scale model was necessary to adequately capture the failure mechanisms in drift ribs, which played a role in sublevel pillar performance. The global model did not provide sufficient resolution to capture drift-scale mechanisms. While the local model was insufficient for calibration of the mine system boundary conditions, the combination of global and local models is valuable in defining mine-scale stress conditions and their impact on local, drift-scale failure mechanisms.

2019 Canadian Geotechnical Colloquium: Mitigating a fatal flaw in modern geomechanics: understanding uncertainty, applying model calibration, and defying the hubris in numerical modelling

“…This data-based justification of increased complexity is required because numerical solutions to geomechanical analyses are often non-unique. In many cases, multiple combinations of input parameters and boundary conditions can result in very similar output, as a demonstrated by Kalenchuk et al (2017). However, the stress-strain paths leading to an ultimately similar end result may be substantially different and influence the fundamental interpretation of the underlying mechanisms.…”

“…Quantitative calibration is exceptionally more difficult to achieve and requires high-quality instrumentation data, as has been demonstrated by various authors (for example, Kalenchuk et al 2017;Crockford et al 2015;Crowder et al 2006). Truly quantitative calibration requires instrumentation to be installed sufficiently early relative to the ground reaction process so that the complete stress-deformation path is captured without significant gaps.…”

Accounting for rock mass heterogeneity and buckling mechanisms in the study of excavation performance in foliated ground at Westwood mine

“…The Westwood Mine is located approximately 80 km west of the town of Val-d'Or in Quebec, Canada. Operations at the Westwood mine were halted by three large-magnitude seismic events that occurred over two days in May 2015, Kalenchuk et al (2017). In addition to these events that caused severe damage to several accesses, other ground behaviours were not well understood, such as the significant discrepancy in the performance of blastholes between secondary and primary stopes and the propagation of damage from stopes to haulage drives in some locations.…”