Improving seismic risk characterisation and management in underground mines

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The mining industry is exploiting deeper orebodies and employing high extraction ratios in order be profitable and competitive. In this context, mining-induced seismicity is becoming increasingly challenging as it poses a significant threat to the safety of mine personnel and to the productivity and economic viability of deep mining operations. The proposed research program aims at advancing the state of knowledge and practice on seismic risk characterisation and management in underground mines. The seismic risk is influenced by the level of seismic hazard, the vulnerability of mine excavations, and the exposure of mine workers. In practice, seismic hazard is defined as the largest seismic event susceptible of occurring within a seismic event population. This research will focus on developing a better understanding of both the larger mine-scale and smaller workplace-scale trends and patterns in seismic hazard. The proposal involves developing a seismic data clustering methodology that would allow for a refined seismic hazard characterization and improved tracking over time and space. The objective is to correlate the level of seismic hazard identified in seismicity clusters with changes in mining-induced stress levels, rock mass properties, and structural geology. Furthermore, temporal patterns in strong seismic responses amongst clusters will be investigated with the objective of improving our understanding of the larger-scale mechanisms involved in generating large magnitude seismic events in mining. Mine blasts are important triggers of mine seismicity, and typically result in periods of increased seismic hazard. In practice, the exposure of mine personnel during these periods is managed through site-specific exclusion and re-entry procedures. These consist in establishing non-entry perimeters and durations to cover periods of anticipated high seismic hazard. The proposed research further involves developing a methodology for assessing the reliability of exclusion and re-entry procedures and characterizing the level of seismic hazard following blasting periods. This has important implications, particularly in the mine development process, which leads to direct exposure of mine personnel to unsupported grounds. The tools that will be developed will have practical implications, such as optimizing the allocation of specialized mining equipment into identified areas of elevated seismic hazard. The proposed research will be conducted in partnership with the mining industry and its resulting applications will aim at directly improving seismic risk management and safety in underground mines. The outcomes will challenge the current state of practice that often requires reactive forensic reviews of past failures in order to adapt mining plans. The training of highly qualified personnel in the field of rock mechanics will address the current needs of the industry, which is deploying important efforts in attracting and retaining these specialists.