Evaluation of alternative ore handling systems on extraction levels of block cave mines

Wayne Scrivens

Research output: ThesisMaster's Thesis (University Course)


Block caving is an underground mining method used to mine massive low grade ore bodies. It can be highly mechanised with high productivity and the lowest cost per tonne of extracted ore of any underground mining method. The development cost is high and the time to ramp up to full production can be several years. As ore bodies close to the surface become depleted, there will be more transitioning to block cave mining underground. Significantly higher production rates will be needed as there will be less high grade ore deposits available with lower amounts of minerals recovered per tonne of ore removed. However LHD productivity is erroded by increased tramming distances for ore bodies with large extraction level footprints. There is a need to investigate more productive and lower cost ore handling and crushing systems on the extraction level of block cave mines. The objective of this project was to provide a study on the potential production improvements from alternative ore handling systems. A LHD production model was created to calculate the productivity and production capacity of a LHD fleet. This was validated using actual production data from a block cave mine. A number of alternative crusher or ore-pass configurations on an extraction level were identified by reviewing existing and planned block caving operations. Using the production model, a comparison was created between these configurations. Ore-passes within the ore body was the most productive and highest capacity configuration for an LHD. This layout is flexible and easier to scale up to suit large footprint sizes. However, it requires the construction of a third level dedicated to haulage by truck, train or conveyor. This increases the construction time, capital cost, operating cost and more ventilation is required. It could also reduce the stability of the extraction level by having additional excavations underneath. While ore-passes can be a hazard, with most injuries associated with the loading and unloading of the ore-pass and removal of blockages or hang-ups. The production rates were calculated for different continuous haulage systems which replace or supplement the LHDs. The equipment requirements of these systems were identified along with the advantages and disadvantages of each concept. The capital costs were estimated and compared along with a Pugh Analysis to help choose between systems. The results of this study show that Mobile Sizer and flexible conveyor combinations have the ability to significantly increase the productivity of the LHD and overall production capacity. There is less development cost from no large excavations and a fleet of sizers are cheaper than large gyrator or jaw crushers. There is also a higher level of redundancy with multiple Mobile Sizers that can be moved around and replaced quickly. This disadvantage of Mobile Sizers is the ability to handle oversize fragmentation. There is considerable potential to increase production capacity using the CAT rock flow system, which scales up the rate of extraction. But the system has a high capital cost and it may take many years to develop into a competitive product. A number of alternative loading equipment designs were reviewed for potential use in a block cave mine. The LHD has an advantage over these other designs due to its low profile, enabling it to work under low roof heights and in confined spaces and its ability to handle large, oversize rock. In the future, it is desirable to keep the loading equipment as short as possible as this dictates the length of the draw point and approach angle. Reducing the length of the draw point and using a 90 degree approach angle will improve the shape of the pillars, increasing stability.
Translated title of the contributionEvaluation of alternative ore handling systems on extraction levels of block cave mines
Original languageEnglish
  • Moser, Peter, Supervisor (internal)
Award date23 Oct 2014
Publication statusPublished - 2014

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