Towards aligning strategic and operational schedules in mining

Abstract

Various schedules are used by mine management to serve specific purposes. The strategic schedule determines the optimal project schedule to maximise the mine's NPV, whilst the operational schedule provides an in-depth operational plan and maximises resource utilisation. Gaps in the literature regarding mathematical models that align the strategic and operational schedules of an underground mine network were identified during the background of this study. The identified literature did not contribute towards the aim of this study; nevertheless, it is relevant for the background. Research has examined aggregating the scheduling calendar timeline to scale the operational schedule to a strategic schedule. The mining literature review highlights this study in explaining the relevant scheduling approaches used for an underground mine network. The relevant optimisation theory used in developing the mathematical model is described in the overview of optimisation theory. This study aimed to align the two schedules with conflicting objectives by developing a strategic schedule with detailed operations. A deterministic Mixed Integer Linear Programming model was proposed to determine the optimal schedule, with an objective function maximising the NPV. The model constraints were verified using a small-scale dataset, and the model results were analysed to determine whether the decision variables were constrained as intended. The mathematical model's performance was analysed to assess its scalability. The model results were compared with a schedule of real operational data on activities for an underground mine network during the validation process. The model improved alignment between project schedules and operational schedules, contributing to the new literature on aligning strategic and operational schedules within a single mathematical model. The MILP formulation of the CSOS model combines strategic scheduling, maximising NPV, with operational constraints that implement resource flows with multiple dynamic sinks and travel durations between activities in an underground mine network. Although the model has poor scalability, the results obtained showed practical improvements over industry heuristics. The research conducted in this study contributes to the literature on aligning strategic and operational schedules, as well as to the literature on a strategic schedule that incorporates short-term operations and travel durations between activities.