New approach to flexible open pit optimisation and scheduling

Résumé En

This paper proposes a dynamic procedure for pit optimisation as the resources become better known and as commodity prices and costs evolve over time. Mining sequences are defined as the quantities to be extracted from each macroblock (rather than small blocks) in each time period. Feasible mining sequences are mining sequences that respect the accessibility constraints, and also the geometric constraints on the amounts that can be extracted from any one block over time, or from all the active blocks at a given time. Having defined feasible mining sequences, their mathematical properties (closure and convexity under certain operations) were studied. Feasible mining sequences are generated randomly. Then a two-step procedure is used to find the best one (or the best few) using three economic criteria. The procedure was tested on a synthetic gold mine based on the characteristics of the Essakane mine in Burkina Faso. The results were encouraging.