Geomechanical evolution of the Nickel Rim South Mine

Glencore’s Nickel Rim South Mine, located in the Sudbury Basin, Ontario, Canada, has been operating at intermediate depths (1,105–1,720 m below surface) since 2007. The mine is ramping down production activities and has transitioned to care and maintenance in July 2024. The mine delivered an unprecedented production ramp-up and has consistently achieved or exceeded the planned life of mine production target while maintaining an excellent safety record. The mine’s achievements are a testament to the mining culture, operational excellence, engineering design, and ground control program. The mine was initially designed with a primary ground support system comprising fibre-reinforced shotcrete and resin rebar, unique to the Sudbury Basin. The project assumption for pre-mining development (first stopes were in 2009) was that the shotcrete and resin rebar support would be sufficient to withstand the potential mining-induced stresses and the associated deformations. However, as mining progressed, it became evident very early in the mining sequence (by 2011) that the original support design basis underestimated the dynamic loading and rockburst risk, which resulted in a fundamental shift in the mine’s approach toward dynamic ground support design. Over the life of the mine, a series of upgrades to the ground support systems were made, including ‘prehabbing’ several kilometres of excavations. The ground support performance is presented with select case studies, highlighting key considerations and limitations of current dynamic ground support design methods. At the time of Nickel Rim South Mine’s inception, there was limited experience with bulk open stope mining in footwall (copper) style deposits within the Sudbury Basin, which was recognised during the initial mine design, resulting in a conservative extraction strategy to manage dilution and associated stope instabilities. As additional data was collected and more experience was gained, the rock mass behaviour of the relatively weak copper veins contrasting with the highly competent host rock became more evident. Underground observations, seismic data analysis, and numerical modelling enabled the mine to adapt to the improved understanding of the rock mass behaviour and implement significant strategic changes to the original mine design. Key strategic changes are presented, with discussions on the geomechanical back analyses and the realised operational flexibility. This paper presents key strategic and tactical controls utilised to manage seismic hazards and rockburst risks at Nickel Rim South Mine and compares the final implementation to the initial geomechanical assessment of these controls. Generally, there is a significant gap in the knowledge of rock mass behaviour in the infancy of a mine, which is often bridged with assumptions and empirical rules. An important consideration is that most empirical design approaches and guidelines are based on shallow mines and may not necessarily translate to mines at greater depths. The paper also promotes discussions on what this might mean for future deep mining operations as well as emphasises the necessity of a robust and effective ground control program that not only considers and manages ongoing operational geomechanical risks but also systematically validates and challenges the original underlying design assumptions based on observed and measured rock mass behaviour to inform and support the optimisation of the mine design.

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