Traditional and New MIP Models for Production Scheduling With In-Situ Grade Variability

Abstract

Mixed integer programming (MIP) has become a common approach for optimizing production schedules of open pit mines since the 1960s. However, MIP has been found to be limited by: (a) feasibility in generating optimal solutions with practical mining schedules; and (b) inability to deal with in-situ variability of orebodies. In looking into these shortcomings, this paper presents a general production scheduling method for multi-element deposits in open pit mines. The method is subsequently used to optimize the production schedule in a nickel laterite deposit. The application confirms the weaknesses of MIP formulations mentioned above. An alternative MIP formulation is then presented and applied to the same deposit. The results of the new formulations show that the new MIP model can overcome the above shortcomings and generate practical mining schedules with a higher chance of achieving planned production targets than traditional MIP schedules.