Concurrent optimisation of open pit ore and waste movement with optimal haul road selection

Optimal open pit ore and waste scheduling with a network of haulage options create a large combinatorial problem. In this paper, a mathematical model has been proposed to simultaneously optimise pit and waste dump schedules with the shortest haulage selection from possible haul-road networks. The model also determines the optimal quantity of material to be sent through the shortest haulage path for all combinations of sources and destinations. This is a new approach of simultaneous optimisation as earlier studies had optimized pit, dumps and haulage separately missing their combined impact on optimality. The new model has been implemented on several case studies detailed in the paper. A comparison has been performed for a case study which revealed that 39% savings in haulage distances and 44% savings on backfilling to in-pit dumps over a schedule using a mine planning software. Furthermore, different case studies have been solved using an exact as well as a meta-heuristic method developed for the purpose and the results of both methods match within close limits and whereas the meta-heuristics showed a considerable improvement in solution time as data size increased.