Pit optimisation and life of mine scheduling for a tenement in the Central African Copperbelt

Abstract

Open pit optimisation and scheduling tasks are an important part of mining ventures that have attracted considerable attention in the mining industry in the past couple of decades. The process of determining the optimum pit significantly impacts the calculation of mine life, which involves huge capital investment. This paper addresses the application of a heuristic algorithm for optimising the pit size and then life of mine scheduling for a copper-cobalt deposit in the Central African copper belt. The resource model was generated using a traditional geostatistical algorithm, specifically the kriging method. The methodology used was to generate a series of optimised nested pits by artificially varying the commodity price and applying a graph closure algorithm. The mine scheduling was generated by combining the solutions of different sub-problems. The deposit is optimised to 9.1 Mt with an average copper grade of 2.03% and cobalt grade of 0.47%. The total NPV generated from the pit is around 495 million US dollars. The results of our proposed algorithm were compared with linear relaxation of the mine scheduling problem. They demonstrated that our proposed algorithm is 30 times more efficient than the linear relaxation problem with an optimality gap of 7.4%.