An Uncertainty-based Transition from Open Pit to Underground Mining

Document Type : Original Article


Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran, Iran


There are some large scale orebodies that extend from surface to the extreme depths of the ground. Such orebodies should be extracted by a combination of surface and underground mining methods. Economically, it is highly important to know the limit of upper and lower mining activities. This concern leads the mine designers to the transition problem, which is one of the most complicated problems in mining industry. The transition problem is categorized as a strategic one and is formulated in the form of long-term production scheduling problems. This implies that the transition problem is highly affected by the uncertainties that are rooted in the quantity and quality of an explored orebody. The current study aims to evaluate the effects of geological uncertainty on transition depth. To this aim, an integer programming (IP) model was executed on different simulations of an orebody. The results indicate that the net present value (NPV) of the deterministic solution is greater than that of the basic alternative. However, the uncertainty-based solutions show that the NPV of the whole mining operation is lower than the basic and deterministic solutions mostly (more than 72% of the simulations). Nevertheless, there are some rare cases in which the NPV of the operation may increase ideally up to 2.5 % due to development of the pit bottom downward. Finally, because of a negligible difference between the average NPV of the simulations and that of basic alternative, it is expected that the primitive pit bottom would play the role of transition depth.


Main Subjects

1. Nourali, H., Osanloo, M., "A New Cost Model for Estimation of Open
Pit Copper Mine Capital Expenditure", International Journal of
Engineering, Transactions B: Applications Vol. 32, No. 2, (2019),
2. Mula, J., Poler, R., Garcia-Sabater, J. and Lario, F.C., "Models for
production planning under uncertainty: A review", International
Journal of Production Economics, Vol. 103, No. 1, (2006), 271-285. 
3. Vallee, M, "Mineral resource + engineering, economic and legal
feasibility = ore reserve", Canadian Mining and Metallurgy Society
Bulletin Vol. 93, (2000), 53–61. 
4. Jamshidi M, Osanloo M., "Reliability analysis of production schedule
in multi-element deposits under grade-tonnage uncertainty with multidestinations
for the run of mine material". International Journal of
Mining Science and Technology (2018). 
5. Groeneveld, B., Topal, E., "Flexible open-pit mine design under
uncertainty", Journal of Mining Science, Vol. 47, No. 2, (2011), 212226.
6. Rahmanpour, M., and M. Osanloo. "Resilient decision making in
open pit short-term production planning in presence of geologic
uncertainty." International Journal of Engineering, Transactions
A: Basics, Vol. 29, No. 7 (2016), 1022-1028. 
7. Montiel, L., Dimitrakopoulos, R., " A heuristic approach for the
stochastic optimization of mine production schedules", Journal of
Heuristics, Vol 23, (2017), 397–415, DOI 10.1007/s10732-017-93496.
8. Azimi, Y., Osanloo, M. and Esfahanipour, A., "An uncertainty based
multi-criteria ranking system for open pit mining cut-off grade
strategy selection", Resources Policy, Vol. 38, No. 2, (2013), 212-223. 
9. Gholamnejad, J., Osanloo, M. and Khorram, E., "A chance
constrained integer programming model for open pit long-term
production planning", International Journal of Engineering,
Transactions A: Basics, Vol. 21, No. 4, (2008), 307-318. 
10. Popover, G. (1971). The working of mineral deposits (Translated
from the Russian by Shiffer, V.). Mir publishers, Moscow, (1968),
11. Soderberg, A., Rausch, D.O. Surface Mining (Section 4.1). Pfleider,
E.P., (ed.). AIMM, New York. 142–143. 
12. Chen J. Li, J., Luo, Z., Guo, D. Development and Application of
Optimum Open-Pit Limits Software for the Combined Mining of
Surface and Underground. CAMI, (2001), 303−306. 
13. Chen, J., Guo, D., Li, J. Optimization Principle of Combined Surface
and Underground Mining and Its Applications. Journal of Central 
South University of Technology, Vol. 10, No. 3, (2003), 222−225. 
14. Bakhtavar, K. Shahriar, K., Mirhassani A. Optimization of the
Transition from Open Pit to Underground Operation in Combined
Mining Using (0-1) Integer Programming. Journal of the Southern