Optimisation of shovel-truck haulage system in an open pit using queuing approach

Abstract

Open-pit mining operations involve loading and hauling of material from the pit to the processing plant or waste dump depending on the ore grade. These two activities account for more than 50% of total operating costs of the mine. There are several loading and hauling systems that are employed depending on the geometry of the ore body. This study applies a shovel-truck haulage system in a limestone open-pit mine to optimise the productivity of the plant using queuing theory technique. This study developed a model using Mat-lab software to calculate the inter-arrival rate and service rate for different numbers of trucks subjected to the same haulage system. The current system used at the limestone cement plant quarry has an inter-arrival rate of 24 trucks/hour and a service rate of 10 trucks/hour with 16 trucks and 2 shovels in the system. Using this data on the developed model, it is evident that when the number of trucks increases to 12, the system daily production increased up to an optimal point of 7644.52 tonnes/day. Thereafter, an increase in the number of trucks reduced the truck productivity, hence reducing the system production and increasing the cost per tonne of material hauled.