Browsing by Author "Tati, Buntu Bantu"

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    Support Design for Wide Stoping Heights Resulting from Footwall Lifting of Previously Mined Merensky Panels
    (University of the Witwatersrand, Johannesburg, 2024) Tati, Buntu Bantu
    This research report is based on project work conducted at Impala Platinum Mine No. 20 Shaft. The purpose of the project was to provide suitable support and an extraction sequence to mine a mineralized zone in the footwall of previously mined Merensky Reef stopes. An estimated 1.4 kt of ore was available at an average grade of 1.75 g/t (68 000 ounces) at this shaft. A geotechnical investigation was done to gain an understanding of the footwall Pegmatoid mineralization as well as the structural characteristics of the rockmass. A footwall lifting method needed to be developed that incorporated a support system that was based on sound design principles. A tendon and cement pack support system was determined through both a deterministic and a probabilistic key block approach. The support design was limited to local pane support and did not include pillar behaviour. Cable anchors were the selected replacement units for timber elongates removed by the footwall extraction method. A cable anchor length greater than the anticipated fall- out height of 1.77 m was required. The analysis showed that the support length had a much smaller effect on rock fall-out results than the support spacing. Cable anchors spaced 1.5 m x 2.0 m with a length of 2.5 m were determined to be the optimal support configuration for stability. Despite this finding, only 3.5 m long cable anchors were readily available at the No 20 Shaft and were subsequently used in the trial. The Trench and Retreat Mining Method was used in the trial over three months. During this period, a proof of concept was developed for the support and extraction method. Various recommendations are provided in this report to enhance the methods and better optimise extraction in the long term.