Abstract
Vale Canada Limited has been operating many underground mines in the Sudbury basin for over a century and all mines have experienced a significant increase in the number of major seismic events over the last decade. Various mitigation strategies have been developed at Vale’s North Atlantic Operations in Ontario to manage and control the risks associated with seismicity and rockbursts over the last decade. Recent data analysis at all mines reveals that although the number of major seismic events has increased over time, the number of rockbursts has exhibited a decreasing trend in recent years. This paper will illustrate the trends of major seismic events (>1.0Mn) and rockbursts over the last decade with a discussion of their related triggering mechanisms. Most importantly, the paper will focus on the evolution of Seismic Risk Management Strategies developed over the last decade, including both strategic and tactical control measures. Specific topics include: change of mining method and mine design in open stoping and cut and fill operations, de-stress blasting in development headings, destressing strategies for sill/diminishing pillar areas, Seismic Hazard Maps, Re-entry protocol after major seismicity, the use of appropriate equipment to eliminate the exposure of personnel in highly burst-prone ground conditions, dynamic and enhanced ground support systems, development face ground support systems, the formation of an external Seismic Review Board (SRB), the establishment of 3D geological and structural models and internal technical assurance/reviews managed through a Corporate Geotechnical group. Some case studies will be presented in the paper to demonstrate increased effectiveness of the control measures over the last decade. Future research directions associated with the development of strategies to mitigate the hazards associated with seismicity and rockbursts will also be presented.