Sensitivity Analysis to Evaluate Haulage Systems Selection for Underground Mines Using Discrete Event Simulation and Mixed Integer Programming*

Abstract

As deposits located in near surface continue to be mined out, the mines will focus on deeper operations whereby the haulage distance to the mine surface is going to be one of the main challenges. Several haulage systems such as diesel and electric-powered trucks, shaft, and conveyors can be utilized for hauling operations at shallow or great mine depth. When they are to be used for longer haul distances to the mine surface, the haulage methods with less operating costs will be beneficial towards cost reduction. To improve the decision making, the haulage selection processes require knowledge of the mine planning, scheduling under variable parameters. Therefore, this paper presents a sensitivity analysis to analyse the effects of changes on selected parameters on the net present value (NPV) of the mine plans generated for an orebody at 1000- and 3000-meters levels for diesel and electric-powered trucks, shaft, and belt conveyor haulage methods using discrete event simulation and Mixed Integer Programming to evaluate the most sensitive parameters on the selection of haulage operations as mine depth increases. The simulation analysis aimed to assess the performance of these haulage options in achieving the production target of 100,000 tonnes of ore per month for each option at each depth. The simulation results were used to determine the energy cost per tonne of each haulage scenario for each depth and then exported to the mixed integer programming to calculate the operating cash flows to generate an operating NPV. The results show that, in hauling of material from underground to mine surface, diesel trucks are only feasible at shallow depth, while electric trucks, shaft, and conveyor belt systems can be used for longer haul distance. It also indicated that, diesel-powered trucks are observed to have low NPVs compared to other haulage options, while shaft and belt conveyor generated high NPVs with increasing mine depth. It is therefore concluded that, mine planners can minimize risks when evaluating haul methods, and use sensitivity to guide a suitable choice and flexibility on the hauling operations.