Considerations for open pit to underground transition interaction

Hamman, Emrich; Cowan, Matthew R.; Venter, Julian; Souza, Juliano de

doi:10.36487/acg_repo/2025_74

Cited by 5 publications

(2 citation statements)

References 9 publications

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“…To address these concerns, we conducted a parametric study to investigate the design and influence of the stope, not only in the vicinity of the excavation but also in relation to open-pit displacement, particularly at the pit bottom and pit walls in the Sepon gold mine. According to the classification in the previous report [23], the transition scenario can be categorized into three types. The first involves transitioning from open-pit mining to underground mining, where both operations are carried out simultaneously.…”

Section: Introductionmentioning

confidence: 99%

A Stope Mining Design with Consideration of Hanging Wall When Transitioning from Open Pit Mining to Underground Mining for Sepon Gold Mine Deposit, Laos

Phaisopha,

Shimada,

Sasaoka

et al. 2023

Mining

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This study investigates the transition from surface to underground mining at the Sepon Gold mine. The stability of surface slopes is assessed prior to commencing underground operations. Stope mining is adopted based on ore body characteristics and geological features. Finite element numerical analysis, employing the Generalized Hoek–Brown criterion, evaluates slope stability for surface slopes and opening stopes. The pit design comprises a 70° slope angle, 20 m height, and 10–15 m safety berm, meeting stability requirements with a factor of safety of 2.46. Underground mining design includes a 62° ore body dip, a 50 m thick crown pillar to prevent surface subsidence, and 5 m wide, 5 m high stopes. Sill pillars are left for support after each level of excavation. Rock bolts are employed in specific stope areas where necessary, with continuous monitoring for surface deformation. This study analyzes the influence of stope sizes on the pit wall and pit bottom stability, identifying slope failures near the hanging wall close to the pit bottom during underground mining. A slight increase in the displacement zone is observed on the upper crest of the top footwall. Overall, the findings demonstrate successful stability in the transition from surface to underground mining at the Sepon Gold mine.

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Section: Introductionmentioning

confidence: 99%

A Stope Mining Design with Consideration of Hanging Wall When Transitioning from Open Pit Mining to Underground Mining for Sepon Gold Mine Deposit, Laos

Phaisopha,

Shimada,

Sasaoka

et al. 2023

Mining

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“…With the integration of underground mine below, it is most likely that the geotechnical challenges associated with the slope be worsened. Hamman et al (2020) classify transition scenarios into three namely 1. Open pit transitioning to underground, where there will be simultaneous operation of OP and UG for some period before OP closes 2.…”

Section: Introductionmentioning

confidence: 99%

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

Dintwe¹,

Sasaoka²,

Shimada³

et al. 2021

GEP

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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.

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