Authors: Beruar, ONS; Yao, M; Sampson‐Forsythe, A

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Beruar, ONS, Yao, M & Sampson‐Forsythe, A 2012, 'Challenges in multiple sill pillar mining at Vale’s Coleman Mine', in Y Potvin (ed.), Deep Mining 2012: Proceedings of the Sixth International Seminar on Deep and High Stress Mining, Australian Centre for Geomechanics, Perth, pp. 297-310,

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At Vale’s Coleman Mine in Sudbury, Ontario, Canada, multiple diminishing sill pillars exist in the main orebody. The top most sill pillar known as MOB1 (Main Orebody 1), is immediately below a previously mined out area of neighbouring Xstrata’s Fraser Mine and the other two sill pillars MOB2 (Main Orebody 2) and MOB3 (Main Orebody 3) are between two cut and fill (CAF) areas currently being mined at Coleman Mine. All together these sill pillars contain approximately five million tons of ore. An engineered stope sequencing is important for the successful recovery of the sill pillars. As per the current production schedule, there is some overlap in the timing of mining these sill pillars; therefore, mining in one sill pillar will have an influence on the rock mass response in the other sill pillars. As mining progresses, some areas will become stress shadowed, while others will be highly stressed. Managing the changing stress conditions is expected to become increasingly challenging. Recovery of the sill pillars will be executed by longhole/blasthole stoping methods. Maintaining the access to the stopes will be a challenge and will require a sound ground control strategy to deal with changing stress conditions. This paper examines the impact that mining one sill pillar will have on the other sill pillars and proposes tactical geomechanics guidelines to meet the mine production schedule and maximise recovery. The MAP3D boundary element program for numerical stress modelling has been calibrated against field conditions and subsequently used to determine the optimum mining sequence to ensure that these sill pillars can be safely and efficiently recovered. In addition, the development and ground support strategies for the top and bottom sills of the blasthole stopes have also been discussed.

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