Access Optimisation Tools in Underground Mine Design

Optimisation tools which determine the best layout for access and haulage in an underground mine address an important and difficult mine design problem. The complexity of the problem can be compared to the task of optimising the final pit design in an open pit, together with the pit haul roads required. The strategic design of an underground mine layout must address the location of haulage shafts, decline access, ventilation infrastructure, level development within the stopes, and stope access. By calculating optimal layouts corresponding to a range of cut-off grades, the economic viability of the various mining areas can be assessed, and the results may be a significant factor in maximising the net present value of the mine. At the University of Melbourne, two software tools have been developed to address this problem: the Planar Underground Network Optimiser (PUNO) and the Decline Optimisation Tool (DOT). PUNO minimises the total production costs associated with the level layout within an orebody, using the theory of weighted Steiner networks. DOT optimises the haulage decline (or declines) under a reasonably comprehensive set of constraints, including turning circle, gradient and the avoidance of “no-go” regions. Both PUNO and DOT minimise total cost of development and haulage. This paper discusses the use of such tools as part of the mine planning process, and the methods underlying them. The tools have been applied in a number of industry case-studies. The long-term aim is to integrate the access design with other design tasks, such as stope optimisation, mine scheduling and strategic options evaluation.