Development of a laboratory wheeltracking test for unbound granular material characterisation

To develop performance-based specifications for unbound granular materials, new laboratory wheel-tracking equipment has been developed in the context of Austroads research project. The equipment allows for compaction and wheel-tracking of slab specimen. The specimen is compacted under a segmental steel wheel, to simulate field compaction. The central part of the slab is compacted evenly and is not affected significantly by the edge effects as shown by density measurements. In tracking mode a wheel is fitted with a large pneumatic tyre to enable the rut-resistance of pavement materials to be determined under rolling wheel loads. The surface deformation of the specimen is automatically monitored by a built-in laser scanning system. Validation of the compaction process and the sample preparation method are summarised, as well as a few initial wheel-tracking results.