Abstract
There are many deposits that have the potential to be mined by a combined method of open-pit and underground. In this manner, the most sensitive problem is the determination of the optimal transition depth from open-pit to underground or vice versa. To calculate this depth, a model based on block economic values of open-pit and underground methods together with the Net Present Value (NPV) attained through mining is first presented. During the model, NPV of open-pit is compared to the value of underground for the similar levels. A hypothetical example is used in order to analyze the model in detail. Based on the assumptions made such as: a discount rate of 15 %, each pair of contiguous level-cuts have to mine during one year, and one level as the height of crown pillar, the optimal transition depth was determined to be equal to 62.5 m. Then, level 6 was considered as the suitable crown pillar. Finally, maximum total NPV of the combined mining was calculated to be 25.54 units of currency.
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Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 5, pp. 86–94, September–October, 2009.
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Bakhtavar, E., Shahriar, K. & Oraee, K. Transition from open-pit to underground as a new optimization challenge in mining engineering. J Min Sci 45, 485–494 (2009). https://doi.org/10.1007/s10913-009-0060-3
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DOI: https://doi.org/10.1007/s10913-009-0060-3