Investigation and determination of the required optimal width of overlap between rings on sublevels at LKAB Malmberget mine

Authors: Gyamfi, S; Wettainen, T Download Paper

Cite As:
Gyamfi, S & Wettainen, T 2024, 'Investigation and determination of the required optimal width of overlap between rings on sublevels at LKAB Malmberget mine', in Daniel Johansson & Håkan Schunnesson (eds), MassMin 2024: Proceedings of the International Conference & Exhibition on Mass Mining, Luleå University of Technology, Luleå, pp. 749-759.



Abstract:
The sublevel caving mining method as the name implies, involves the extraction of the ore from sublevel to sublevel progressing downwards. The width overlap is essential for a safe sequential order of mining (by not creating pillars or bridges of intact rock that may attract seismicity), as well as maximizing ore extraction at lower levels without causing any disturbance to the material flow and SLC functionality. This article describes the investigation and determination of the required optimal width of overlap between rings when planning the production drilling at LKAB Malmberget mine. The determined width of overlap was based on the assessment of a specific active production location in the mine where there is a possible residual pillar between levels that will likely create seismicity and other related problems. The assessment revealed an optimal width overlap as, the number of rings to connect the opening of the drift directly at two levels above plus [Equation] multiplied by the total blasted ring length of that same drift. The overlap = [Equation] represents a safety factor for optimal overlap and maximum recovery, and it determines the ideal overlap width, which is relative to the two levels above. The results, as well as other factors that could affect the optimal width of overlap, have been discussed and specific recommendations for the application and implementation of the assessment have been suggested.