Evaluation of mine design options for the Nkana synclinorium mining project: a case study of Mopani copper mines, Zambia.

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Nicacio, Hugo
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The University of Zambia
Mining method selection is one of the most critical activities of Mining engineering with the ultimate goal of maximizing profit, mineral recovery and arrive at a method with the least problems among feasible alternatives. The geology at the Synclinorium is complex with four main lithologies i.e. SOB Shale, Hanging Wall Argillite, Near Water Sediments and the Upper Quartzite, folded with variable thickness. A critical geological feature is the foliation or bedding that replicate the folding along the strike of the ore body. This poses a challenge in terms of selecting a suitable mining method for this ore body that will be less costly with high recoveries and low dilution. The main aims of the research were to select a suitable mining method, identify the current challenges encountered in the existing mining methods and carry out an economic evaluation of the Synclinorium mining project. The methodology used in data collection involved underground visits to various sections of the mine to understand the geology, rock types, orientations and geological discontinuities, current mining methods and associated challenges. Others involved a review of research works on underground mine planning and design, literature on mining method selection, mining journal and research done by Murray and Roberts and SRK consulting firms on the design. Detailed discussions on the input parameters for mine design with mine planning, geologists, geotechnical engineers, senior mining officials and cost accountants were undertaken to understand the current cost of mining. Diamond drilling and logging of borehole core was also conducted. The results gathered were then subjected to mine design criteria for selecting a mining method. In this research, University of British Colombia (UBC) mining method selection criteria, online mining method selection tool (MMST) and fuzzy dominance methods were used for the selection of a suitable mining method. These methods reviewed that, Sublevel stoping, Cut and fill, Sublevel caving and Block caving were selected in that order. However, after subjecting the selected mining methods to geotechnical, technical and economic evaluation, Sublevel Open (SLOs) stoping with fill in the anticline, Sublevel caving (SLC) in the limbs and VCR in the synclines were recommended. The current SLC and Vertical crater retreat methods require modification to address the current challenges due to hang-ups, delayed hanging wall exposure and creation of a huge void prior to hanging wall collapse as mining progresses and hole deviations in VCR at 50m that results in re-drilling and ultimately increase the costs of mining. The economic evaluation indicates that the Synclinorium mining project is viable with a projected average annual income of $340million.
Thesis of Master of Engineering Degree in Mining Engineering (M.Min.Sc)