Analytical study of performance models for unbound granular pavements

This report presents an analytical and parametric study to assess the relevance of rutting performance models for unbound granular pavements. The rutting performance relationship used in the Austroads Guide to Pavement Technology Part 2 – Pavement structural designdoes not take into account the performance of each granular layer and the subgrade and globalises the whole pavement deformation. The deformation of the base layer can significantly contribute to the total pavement deformation and is not evaluated separately from material performance parameters. A new performance based framework for rutting prediction allowing model calibration on wheel-tracking tests and pavement prediction has been built. The reports presents a validation of the calibration stage from experimental data obtained with the new wheel-tracker developed for unbound granular materials. For simple pavement configurations, the base deformations are calculated and highlight the difficulties in extrapolating laboratory to pavement performances. The model is used to calculate the relative performance factors obtained for changes in base thickness, subgrade stiffness and axle mass. The parametric analyses conclude consistency of the trends obtained when the pavement configuration and loading are modified and support further development toward validation. In the future the Austroads project TT1819 will provide the data available to validate the framework approach for road base deformation modelling.