Optimising pillar design for enhanced safety and productivity in underground coal mining in Zimbabwe

The growing demand for coal in Zimbabwe’s industrial sector has necessitated the shift to underground mining as surface reserves become increasingly depleted. However, underground mining introduces substantial risks due to the formation of unstable voids, which, if not adequately supported by pillars, can result in catastrophic failures, such as the historic Coalbrook Colliery disaster. To mitigate these challenges, effective pillar design is critical for ensuring both ground stability and economic feasibility. This study adopts a multifaceted approach to balance operational safety with economic sustainability. Empirical design methods, including the Tributary Area Theorem and the Van der Merwe formula, were initially applied to determine appropriate pillar dimensions. These were further evaluated and refined through numerical modelling techniques using Phase2 software to enhance stability predictions. Key performance indicators, such as the safety factor and the economic extraction ratio, were analyzed to assess the design’s structural integrity and profitability. The results underscore the significance of optimized pillar configurations in reducing stress concentrations and preventing structural collapses. By integrating empirical and numerical techniques, this study presents a robust framework for the design of safe and cost-effective pillar systems in Zimbabwe’s underground coal mines. These findings contribute to safer mining practices while supporting the nation's increasing energy requirements.