Production scheduling under uncertainty of an open-pit mine using Lagrangian relaxation and branch-and-cut algorithm. Issue 5 (27th May 2020)

• Record Type: Journal Article
• Authors: Chatterjee, Snehamoy; Dimitrakopoulos, Roussos
• Is Part Of: International journal of mining, reclamation and environment. Volume 34:Issue 5(2020)
• Page Start: 343
• Page End: 361
• Publication Date: 2020-05-27
• Subjects: Open pit mine optimisation -- production scheduling -- uncertain supply -- Lagrangian relaxation -- sub-gradient method -- branch and cut algorithm; Mining engineering -- Periodicals; Mineral industries -- Environmental aspects -- Periodicals; Abandoned mined lands reclamation -- Periodicals; 622.292
• DOI: 10.1080/17480930.2019.1631427
• Languages: English
• ISSNs: 1748-0930

Abstract

ABSTRACT: The life-of-mine optimization of open pit mine production scheduling under geological uncertainty is a computationally intensive process. Production scheduling determines the optimal extraction sequence by maximizing net present value (NPV). In this paper, an algorithm is proposed to schedule an open pit mine under geological uncertainty, where instead of solving the whole problem at once, the production schedule is generated by sequentially solving sub-problems. The sub-gradient method is used to generate the upper bound solution of a Lagrangian relaxed sub-problem. If the upper bound relaxed solution is infeasible, a mixed integer programming is applied to the latter solution. The algorithm is validated by solving six problems and is compared to the linear relaxation of the original production scheduling problem. The results show that the proposed algorithm generates a solution that is very close to optimal, with less than a 3% optimality gap. An application at a copper mine, where geological uncertainty is quantified with geostatistical simulations of the related orebody, shows that all constraints are satisfied and an 11% higher NPV is generated when compared to the corresponding deterministic equivalent of the proposed approach, while a 26% higher NPV is generated compared to a common conventional industry approach.