Optimizing Open Pit Block Scheduling with Exposed Ore Reserve

A crucial problem in the mining industry is to determine the optimal sequence of extraction of blocks, in which the mine has been structured for exploitation. Typically a mine can be constituted by several thousands or millions of blocks. The sequencing models for this structure are very complex giving rise to very large combinatorial linear models. Operational mine plans are usually produced on a yearly basis and further scheduling is attempted to provide monthly, weekly and daily schedules. A portion of the ore reserve is said to be exposed if it is readily available for extraction at the start of the next period. In this paper, an integer programming model is presented to generate pit designs under exposed ore reserve requirements, as an extension of the classical optimization models for mine planning. For this purpose, we introduce a set of new binary variables, representing the extraction, wasting and processing decisions. The model has been coded and tested in a set of standard instances, showing very encouraging results in the generation of operational sequences of extraction and destination of blocks.