Influence of vertical load and tyre type on the performance of unbound granular pavements

The purpose of this paper is to summarize a new technical research project as well as analysis and findings of the assessment of the impacts of axle mass increases and tire types on road deterioration for sprayed seal surfaced unbound granular pavements, the most common pavement type in Australasia. ARRB Research is currently undertaking an Austroads technical research project: ‘Influence of vertical loading on the performance of unbound and cemented materials’. Two specific objectives of the research are to determine load damage exponents (LDEs) and to assess the relative damaging effects of wide single tires and steer axle tires compared to dual tires for Australasian pavement types. The reference load on a steer axle with 295/80R22.5 single tires which was estimated to cause the same pavement wear (vertical surface deformation) as an 8.2 ton standard axle fitted with dual 11R22.5 tires was found to be 5.4 ton, which is in good agreement with the Austroads Pavement Design Guide.