Abstract
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.
Highlights
The lifetime of a mine may be extended by transitioning from open pit (OP) mining to underground (UG) mining
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
Stability of the slope under the actual conditions was monitored during the underground mining, the displacement, stress and yielding zones of the slope section are presented in Figures 3-5 respectively
Summary
The lifetime of a mine may be extended by transitioning from open pit (OP) mining to underground (UG) mining. The steepened high slope walls generally threaten the structural integrity of the pit and lead to instabilities. While considering the viable underground mining, presence of the open pit structure over the underground mine presents not just new but rather complex challenges ranging from surface subsidence, slope deformation, mud rushes, and crown pillar collapse to underground instabilities. Ernest Henry mine, Australia, suffered from high slope deformations as the wall collapsed due to sublevel caving below open pit mine (Campbell & Lilley, 2018). The control is not just limited to the geological structures, and the geometry of the pit could as well influence the slope failure in response to underground mining. The numerical model simulation intends to decipher various possible scenarios relating to open pit geometry, overall slope angle (OSA), and overall slope height (OSH) effects in response to underground mining
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call