A Field Study on Haul Time Variability in Open Pit Mines
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As open pit mines get larger and their road networks more complex, haul road traffic is an area of increasing concern for mine operators. In particular, engineers from Barrick Gold Inc. have observed haul truck interactions in some of their larger open pit mines that are clearly disruptive to the haulage cycle. Such traffic effects cause uncertainty in haul times over identical routes and commercial dispatch systems do not explicitly account for this variability. This research, based on first-hand data collected from the Goldstrike Open Pit in Northern Nevada, focuses on assessing the level of variability in haul times, identifying the sources of said variability, and determining the effects on haulage optimization. Initial data analysis shows different levels of variability over the range of observed haul times, and further investigation identifies certain haulage parameters as significant sources of said variability, such as road topography and intersection effects. Focusing on these areas of interest, relevant data sets were manipulated to reduce levels of data dispersion and compared to observed results in order to quantify the effects in terms of changes to overall mean haul times along identical routes. It was observed that variability has a negative impact on travel times and moderate variability reduction was observed to increase productivity by 1–2 % when used as an input to a simple dispatch simulation program based on the Goldstrike Open Pit.