Open-pit phase design considering operational constraints: Towards the generation of high adherence production planning policies

The conventional method for formulating open-pit mine production strategies suffers several drawbacks. One of them is that the generation of the extraction sequence is done in separate stages and does not consider the temporality of the extraction and processing decisions, so it does not maximize the net present value. In addition, the solutions obtained are difficult to implement because they do not ensure minimum operating spaces for the use of large mining equipment. Consequently, the process is performed sub-optimally. This work proposes a novel methodology to address the open-pit phase design under a mathematical programming approach. For this, an integer program generates phases that maximize an approximation of net present value and satisfy (i) minimum geometric spaces between phases and (ii) minimum and maximum capacities of the mining operation per phase, aiming for practical open-pit mine production planning policies. This methodology was applied in a case study, and the results show its ability to generate practical phases, obtaining differences in net present value lower than 2.02% compared to an optimization approach that does not consider these operational constraints. Therefore, the proposed open-pit mine extraction policy significantly improves its operational design without considerably affecting the expected value promise.