Evaluation of alternative mining sequences with consideration of barrier pillar placement at LKAB Kiirunavaara mine

Authors: Rentzelos, T; Andersson, J; Sjöberg, J; Jonsson, L; Dahnér, C; Swindell, R; Kulcsar, Z Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2465_16

Cite As:
Rentzelos, T, Andersson, J, Sjöberg, J, Jonsson, L, Dahnér, C, Swindell, R & Kulcsar, Z 2024, 'Evaluation of alternative mining sequences with consideration of barrier pillar placement at LKAB Kiirunavaara mine', in P Andrieux & D Cumming-Potvin (eds), Deep Mining 2024: Proceedings of the 10th International Conference on Deep and High Stress Mining, Australian Centre for Geomechanics, Perth, pp. 327-340, https://doi.org/10.36487/ACG_repo/2465_16



Abstract:
In May 2020 the largest mining-induced seismic event in Sweden to date occurred at the LKAB mine in Kiruna. The event caused significant damage along several hundreds of metres of drifts in the mine in the area known as block 22. Following the event, LKAB permanently stopped the production in the affected area, leaving in place a permanent barrier pillar splitting the Kiirunavaara Mine into a north and south mine. The dimensions of the barrier pillar were determined in a previous study to be about 600 m wide and 350 m high. Preliminary placement was based on minimising ore loss but a more precise adjustment with respect to local geology and rock mechanical aspects remains. Moreover, the current mining sequence must be adjusted with considerations of the barrier pillar for continued mining down to the 1365 m level. A previous study has shown that mining sequences with a more pronounced V-shape (the so-called chevron sequence) can provide more favourable rock mechanical conditions. The scope of this work involved investigating the interaction of alternative mining sequences with the barrier pillar in its preliminary location as well as identifying the optimal sequence from a rock mechanical perspective. Several possible sequences were examined in a 3D mine-scale numerical model in which detailed lithological units and geological structures have been included. Production has been simulated on a quarterly basis in a model without ‘coupled flow’. The identified sequence was then analysed in a coupled flow model for verification and further analyses of the influence from the sequence on the barrier pillar as well as the surrounding rock and important mining infrastructure. The model results will be used by the mine in the decision-making process for the transition to a long-term sustainable mining sequence.

Keywords: sublevel caving, numerical modelling, mine seismicity, FLAC3D-MassFlow

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