A copy of the presentation made by Minemax at SME 2014 entitled Optimal Open Pit Scheduling with CAPEX and Declining Equipment Capacities is now available for download.
Abstract: We present an open pit scheduling model, implemented in Minemax Scheduler, which finds an NPV-maximizing schedule while accounting for the declining capacity of current and future equipment. Finding optimal solutions to open pit production scheduling problems is a challenge given the large number of blocks, long life of mine, and possibly complex constraints. Annual mining rates are constrained by equipment capacities, which are themselves a function of equipment age. For example, aging trucks require more maintenance, reducing their availability and resultant annual haulage capacity. While modelling the reduction in existing equipment capacity is straight forward, identifying the optimal period in which to replenish capacity via capital expenditures is not trivial as the purchased capacity itself has a declining availability. We posit a solution approach, and present results from a Minemax Scheduler model which implements that approach. Solutions from this model should enable firms to identify better life of mine schedules, more accurately accounting for costs and suggesting optimally timed capital expenditures.