Abstract:

Higher in-situ stresses are expected to induce stronger micro-seismicity as mining production advances to deeper levels. Production setbacks, equipment damage, damage to drift and stopes are some of the potential consequences of strong seismic events. Mining-induced seismicity is influenced by a wide range of mining and geology parameters, most notably, stope dimensions, mining sequence, production rate, and geological structures in the vicinity of the work areas. Analyzing the root causes of strong seismic activities can help better understand the influences of such parameters. It could also prove useful for mine planning to mitigate the occurrence of strong seismic events and to provide a safer work environment. This paper presents a case study of the Young-Davidson (YD) mine of Alamos Gold Inc. in northern Ontario, a gold mining operation using sublevel stoping method with delayed paste fill. The aim is to conduct a comprehensive study of the micro-seismic database to discern the root causes of large micro-seismic events with magnitude?Mn 2.0+ recorded in the deeper mine zone. Moment tensor inversion is carried out to analyze micro-seismicity and identify the mechanisms of rock failure. This helps understand the influence of mining activities and geological structures on seismicity. Event clustering is carried out to identify the trend of fracturing process which is indicative of future hazard locations. In-situ stress measurement previously conducted at the mine are analyzed and used to generate a 3D numerical model, taking into consideration the geological structures specifically the diabase dykes. Mine-wide modelling aims to simulate mining-induced stress distribution per the mine plan of primary and secondary stope extraction. Assessment of stress distribution, brittle shear ratio, and strain energy and comparison with seismic source location, magnitude, and mechanism are presented. This work involves mining, geologic, geotechnical, and seismic data collection and analysis as well as 3D mine-wide numerical modelling. Although the findings from this study are specific to YD mine, they can also be used to elucidate the cause of seismicity at other mines with similar conditions.

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Jacob Francoeur