Optimizing Long‐Term Production Plans in Underground and Open Pit Copper Mines

We present a methodology for long‐term mine planning based on a general capacitated multi-commodity network flow problem formulated as a comprehensive math programming model. The planning methodology considers underground and open pit ore deposits sharing multiple downstream processing plants over a long horizon. The purpose of the model is to optimize several mines in an integrated fashion, though the real size instances are hard to solve due to the combinatorial nature of the problem. We tackle this by solving the relaxed problem of a tight linear formulation and we round the resulting near‐integer solution with a customized procedure. The outcome of this project has been implemented at Codelco, the largest copper producer in the world. Since 2001, the system is used on a regular basis and has increased the net present value of the production plan for a single mine by 5%. Moreover, the integrated approach for multiple mines provided an additional increase of 3%. The system has allowed the planners to evaluate more scenarios. In particular, the model was used to study the option of delaying by four years the conversion of Chiquicamata, Codelco's largest open pit mine, to underground operations