LONG-TERM OPEN-PIT PRODUCTION SCHEDULING THROUGH DYNAMIC PHASE-BENCH SEQUENCING

A long-term open-pit production scheduling method based on the concept of phase-bench sequencing is presented. In this method the state of a n open-pit mine is represented by the number of benches that are mined in each predesigned mining phase (or push-back). Consequently, a spec ific mining schedule can be represented by a sequence of states that s tarts with the topography of the mine site (the initial state) and end s with the ultimate pit (the final state). For a given set of mining p hases all feasible states are first generated and sequences of states are then evaluated for technical and economical feasibility. The best sequence, which gives the maximum net present value (NPV), is found by applying a dynamic programming-based optimization algorithm. The algo rithm also optimizes the cutoff grade that satisfies the mill-feed req uirement for each planning period. It was found that the algorithm can be used not only for scheduling but also as an effective tool for ana lysing the effects of mining and milling capacities and cutoff constra ints on the mining schedule and the total NPV. The algorithm, which wa s programmed in C and run on a Unix workstation, was successfully appl ied to a large gold-copper deposit.