Groupe d’études et de recherche en analyse des décisions

G-2017-94

Stochastic optimization of long-term block cave scheduling with hang-up and grade uncertainty

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The current trend of deeper and lower-grade deposits makes open pit mining less profitable. Mass mining alternatives have to be developed if mining at a similar rate has to be continued. Block cave mining is becoming an increasingly popular mass mining method, especially for large copper deposits currently being mined by open pit methods. This study adopts similar concepts as in stochastic open pit production planning to the planning of block cave mines to evaluate their effectiveness in a different approach to mass mining. The main contribution of this study is the incorporation of the uncertainty of delays from hang-ups and grades directly into the production scheduling process of a cave mining operation. Hang-up uncertainty relates to the uncertainty linked to the occurrence of ore that clogs the production draw points. This clogging causes time delays in the production cycle leading to tonnage losses and additional costs. The grade uncertainty is incorporated by means of stochastic orebody simulations as has been done for years in open pit planning. Both sources of uncertainty are directly linked to the extraction decisions and influence the optimized schedules. The proposed stochastic integer programming model is applied to the optimization of the long-term schedule of a large scale, low-grade copper deposit in a mining complex. The results show the capability of the proposed method to mitigate the influence of hang-up delays by optimizing the extraction schedule.

, 19 pages