Behaviour and support of highly stressed pillars in deep mines and caving operations

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This project aims at assisting mines at great depth (>2km) and mines extracting lower grade ore bodies by caving operations. Caving allows bulk mining of marginal and large ore bodies and is increasingly practiced by mining companies in Canada (e.g., Afton and possibly Diavik mines) and around the world. The proposed research will focus on pillar design with effective, deformable ground support. Experience shows that support installed in hard rock pillars is often ineffective because the support system cannot manage large deformations imposed by the bulking, fractured rock. The researchers will develop, in collaboration with the supporting sponsors, effective tools and techniques to improve pillar design and performance through effective support. It is proposed to focus on three pressing tasks: (1) Deformation-based support selection: matching deformation demand with the support's yield capacity; (2) Development of deformation resistant support components: including assessment of hybrid bolts as potentially the most effective bolts for deformable support systems; and (3) Time-dependent pillar loading: investigating processes resulting from compaction of fragmented rock in and above drawpoints. Effective and efficient support for mining sequences and draw strategies can only be achieved with better understanding of time-dependent load demand, rock deformation behaviour, and capacity of deformation-resistant support. Research approach includes back-analysis of results from physical model tests; in-situ monitoring of extraction level pillars; and in-situ testing of hybrid rock bolts supported by analytical and numerical model developments for reinforced, stress-fractured ground. Findings will assist in arriving at safe and more economic pillar dimensions with cost-effective support. Research will benefit financial and safety performances of Canadian mines, improve understanding of geo-engineering principles for design in stressed ground, and provide valuable opportunities for HQP training at Laurentian University.