Operational methodologies for rolling resistance evaluation

2017

Mr Mark Curley (Research Associate - JPi mine equipment), Dr Tim Grain Joseph (President & Principal Engineer - JPi mine equipment)

The rolling resistance of materials used for haul road construction and to cap in-pit running surfaces is poorly understood and rarely evaluated in practice. Mine waste materials are frequently used to build and cap haul roads, only supplemented by surface capping where better quality gravel or crush materials are available within local geologic and economic limitations. Rolling resistance is most often estimated from limited geotechnical publications, most often made available through mining equipment manufacturer supplemental information whose origin is difficult at best to verify. This paper outlines two methodologies which may be easily employed to evaluate rolling resistance for (a) selection of materials prior to road and running surface planning and construction and (b) an ongoing evaluation of haul road performance, such that critical areas may be identified for more frequent road maintenance or re-build. To select appropriate road building materials, a scale lab test is outlined which highlights the fact that rolling resistance, when expressed as a percentage equivalent slope and hence showing that rolling resistance is independent of haul truck weight and size and as such a material property; may permit not only the selection of individual materials, but may also be used to trial the performance of a composite set of haul road layers’ overall rolling resistance performance as sub-grade layers become deteriorated. The ongoing field evaluation of rolling resistance uses (a) the haul truck as the measurement tool, where each tire is a measurement device, reflected by the load response at the suspension and (b) a cyclic plate load test to establish the resilient pressure stiffness of the ground surface conditions. This permits the ground deformation, which when evaluated in parallel to the tire deformation establishing the changing tire-ground contact area, permits the rolling resistance to be evaluated. In plotting the rolling resistance magnitudes by GPS truck location as the truck moves around the mine site, identifies the critical zones requiring maintenance attention on an ongoing real time basis.
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