LAUSR

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, 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 laboratory test is outlined which highlights the fact that rolling resistance, expressed as a percentage equivalent slope, is independent of haul truck size and hence a material property. It may permit not only the selection of individual materials, but also be used to trial the performance of a composite set of haul road layers’ overall rolling resistance performance as subgrade layers become deteriorated. An 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. The latter indicates 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. Plotting the rolling resistance magnitudes by GPS truck location as a truck moves around the mine site identifies the critical zones requiring maintenance attention on an ongoing real-time basis.