Managing extended tensile zones is more challenging than mitigating or eliminating them during the initial rock engineering design phase. The Witwatersrand basin’s secondary orebody (Kloof Reef) was primarily exploited using robust support (composite packs, 40-ton rock props) to assure the stability of the workings with long mining spans. These rigid (Stiff) supports ensured sufficient support and resistance was applied to the hanging wall to preclude tensile failure, often known as a back break. The current mine is a shallow depth (1900 m) mining, facing a unique challenge for a deep level gold mining. An extended tensile zone in the hanging wall (owing to deadweight, for example) encourages bed separation, resulting in enormous collapse. These large collapses on the hanging wall might happen slowly or quickly, depending on the geological intricacies of the area. The latest sequencing and inclusion of the in-stope pillars (i.e., crush pillars) may respond differently to the current back break challenges. This newly implemented design is an ongoing project that will be monitored as mining progresses.

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Preliminary Case Study on Managing Extended Tensile Zone (Back Break) While Mining in the Deep Gold Mine

  • Richard Masethe,
  • Harold Mohlala,
  • Amoussou C. Adoko

摘要

Managing extended tensile zones is more challenging than mitigating or eliminating them during the initial rock engineering design phase. The Witwatersrand basin’s secondary orebody (Kloof Reef) was primarily exploited using robust support (composite packs, 40-ton rock props) to assure the stability of the workings with long mining spans. These rigid (Stiff) supports ensured sufficient support and resistance was applied to the hanging wall to preclude tensile failure, often known as a back break. The current mine is a shallow depth (1900 m) mining, facing a unique challenge for a deep level gold mining. An extended tensile zone in the hanging wall (owing to deadweight, for example) encourages bed separation, resulting in enormous collapse. These large collapses on the hanging wall might happen slowly or quickly, depending on the geological intricacies of the area. The latest sequencing and inclusion of the in-stope pillars (i.e., crush pillars) may respond differently to the current back break challenges. This newly implemented design is an ongoing project that will be monitored as mining progresses.