Effects of yielding pillars and chevron sequences on convergence and released energy in sublevel cave mining

Authors: Andersson, J; Sjöberg, J; Svartsjaern, M; Töyrä, J; Wimmer, M; Swan, G Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2465_78

Cite As:
Andersson, J, Sjöberg, J, Svartsjaern, M, Töyrä, J, Wimmer, M & Swan, G 2024, 'Effects of yielding pillars and chevron sequences on convergence and released energy in sublevel cave mining', 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. 1193-1206, https://doi.org/10.36487/ACG_repo/2465_78



Abstract:
Yielding pillars have been effectively employed in many underground hard rock mines as a means of support, with pillars designed to yield in a ductile manner to mitigate rockbursts. The concept has so far mainly been applied to cut-and-fill and blasthole stoping with consolidated backfill mining methods. For sublevel cave mining in the LKAB Kiirunavaara Mine, the hanging wall–footwall convergence, over the length of the orebody, is one potential factor that can contribute to release of energy associated with seismic events. By implementing a configuration with large-scale yielding ore pillars, it is theorised that the rate of convergence per mined volume can be reduced, thus also reducing the seismic potential in the mine. To assess the feasibility of this approach, a 3D numerical model was utilised to analyse convergence and energy release effects. The study aimed to demonstrate conceptually, but with a representative orebody geometry, that the proposed mining concept with yielding pillars and a chevron sequence can result in reduced convergence and/or released energy. Four mining scenarios were evaluated, including standard sublevel caving and an alternative chevron-shaped mining front, with and without yielding pillars included. The results suggest that employing yielding pillars could effectively mitigate seismic potential by reducing convergence rates and energy release. However, the specifics of pillar design, including size and recovery, require further investigation. This research and development work contributes to ongoing efforts to improve safety and efficiency in underground mining operations in the LKAB Kiirunavaara Mine.

Keywords: sublevel caving, numerical modelling, mine seismicity, pillars

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