A Decomposition-Based Algorithm for the Scheduling of Open-Pit Networks Over Multiple Time Periods

We consider the multiple time period short-term production scheduling problem for a network of multiple open-pit mines and ports. Ore produced at each mine, in each period, is transported by rail to a set of ports and blended into products for shipping. Each port forms these blends to a specification, as stipulated in contracts with downstream customers. This problem belongs to a class of multiple producer/consumer scheduling problems in which producers are able to generate a range of products, a combination of which are required by consumers to meet specified demands. In practice, short-term schedules are formed independently at each mine, tasked with achieving a grade and quality target outlined in a medium-term plan. Due to uncertainty in the data available to a medium-term planner, and the dynamics of the mining environment, such targets may not be feasible in the short-term. We present, in this paper, an algorithm in which the grade and quality targets assigned to each mine are iteratively adapted, ensuring the satisfaction of blending constraints at each port, while generating schedules for each mine that maximise resource utilisation.