Rutting study of NAPTF flexible pavement test sections

The National Airport Pavement Test Facility (NAPTF) was constructed to generate full-scale testing data to support the investigation of the performance of airport pavements subjected to complex gear loading configurations of new generation aircraft (NGA). The objectives of the NAPTF traffic/performance test program were to explore gear configuration/load and wander effects on pavement responses and performance as a function of number of load applications (N). Two gear configurations, a six-wheel trident landing gear (B777) in one lane and a four-wheel dual-tandem landing gear (B747) in the other lane were tested simultaneously. Transverse surface profile (TSP) measurements and straightedge rut depth measurements were made at regular intervals to monitor the development of rut depth (RD). Using these measurements, a rutting study of the NAPTF flexible test sections was conducted. Statistical tests were performed to consider any difference in mean rut depths between B777 trafficking and B747 trafficking. The rut data were analyzed using the most common surface rutting models (the power model and the third-order polynomial model) and the models were compared. The results showed that the maximum surface rut at the termination of test trafficking is higher for conventional-base flexible test items than for stabilized-base flexible test items. From an engineering standpoint, the mean rut depths accumulated under B777 loading and B747 loading were similar. The number of passes required by the B777 and B747 gears in order to reach a 25.4-mm (1-inch) rut depth. was similar. The power model was statistically significant at the 99% probability level for all of the sections. The third-order polynomial rutting model is a good curve-fitting model, but its engineering significance is questionable. The rutting rate (RD/N) exhibits a linear relation with the number of load repetitions on a log-log scale.