Effects of Sublevel Open Stope Underground Mining on Surface and Open Pit Slopes

Underground mining is an economically viable option for exploiting ore reserves deemed uneconomic after open pit mining. However, underground development can have adverse effects on the above existing open pit slope walls. As a goal of this paper, identification and assessment of potential slope instabilities prior to underground development is crucial for safe and sustainable mining. Towards goal achieving, this paper gives a comprehensive parametric study to investigate the influence of sublevel open stope (SLOS) underground mining on the surface and open pit slope walls. By means of numerical simulation, the SLOS design is tried against the existing open pit followed by adjustments of important slope parameters which are overall slope height (OSH) and overall slope angle (OSA). We found that underground mining may induce slope failure, particularly on the hangingwall side of the pit. Subsidence is prominent on the hanging wall and the surface, whereas, the uplift dominates the footwall and pit bottom. Pit wall closure is observed during underground mining. Although the assigned dimensions in the parametric study show a negligible effect of OSH and OSA, the high OSH experience low subsidence in comparison with low OSH. Overall, the results demonstrate that the slope walls on the hanging wall side are mostly affected by the underground mining and high-stress concentration prevails near slope toes and pit bottom. Additionally, slope deformation decrease from pit bottom towards the slope crest and surface. The results of this study add knowledge to open pit and underground mining interaction.