Integrated optimization of underground mine design and scheduling

It is well recognized that software tools for strategic underground mine planning are lacking, and that the demand for these tools will increase as deeper deposits amenable to underground mining continue to grow in value. While a number of optimization techniques have been developed for stope layout design and progress continues to be made in the area of production scheduling, both of these mine planning areas are amenable to improvement in terms of guaranteeing optimal results. Firstly, stope layout methods struggle to produce truly optimal results and scheduling is hindered by excessive solution times. Secondly, as stated by Chadwick (2009), optimization has the ability to add significant value to a mining operation, but only if the whole process is considered simultaneously, not in isolation as it presently the case. Currently it is common practice for mining engineers to plan each area separately, where the results from one area forms the input data for another. Once planning for each area has been completed, all areas are then combined to form an overall mine plan. To ensure maximum value is obtained from a deposit, however, the three key areas of mine planning – that is stope layouts, development, and production scheduling – must be optimized simultaneously due to the close interaction and influence each area has on the other. This is because improvements made in individual areas do not always translate into total system improvement, as revenues can be reduced or costs transferred elsewhere in the mine plan. Thus, when generating a mine plan, the simultaneous consideration of key individual mine planning areas will yield the best results for any operation (Morin, 2002). This paper reviews some mathematical programming tools that have been developed for optimizing stope layouts and long-term production schedules for underground metalliferous mines. It also highlights studies that have discussed the benefits of using an integrated approach for mine planning. An integer programming (IP) model is presented to optimize stope layout designs and production schedules, which allows for either an integrated or isolated approach to be used. Using both optimization approaches, this model is applied to a gold deposit and the results are discussed comparing the value of the competing approaches. Integrated optimization of underground mine design and scheduling