Rutting development in a flexible pavement structure

A mechanistic empirical (M-E) approach has been developed and used to calculate the degradation behaviour of an arterial road in Southern Sweden. The results were then compared with measurements from the Swedish long-term pavement performance (LTPP) database. The arterial road had reached the critical 15 mm rut after 18 years in operation. The M-E approach used was a two-step procedure where the response of the structure was calculated mechanistically and thereafter the performance predicted empirically based on scaling of laboratory test results. Extensive laboratory testing was carried out on samples taken from the test road. Traffic counting and Bridge Weigh-in-Motion data were used to determine the amount of traffic loading, and data from weather stations were used to take into account the temperature dependency of the asphalt bound layers. The analysis shows that the rutting development can be simulated adequately although the calculations show a slower rate than the measurements towards the end of the simulated period. The discrepancy in the rate of rutting between the measurements and the observations that was observed after about 9 years of operation might be due to the fact that no ageing, seasonal variation including the spring thaw period or changes in structural integrity of the pavement structure were incorporated in the numerical analysis but surely observed in reality.