Predicting Rutting Performance of Pavement Granular Layers at the FAA’s National Airport Pavement Test Facility

After the first round of testing at the Federal Aviation Administration’s (FAA’s) National Airport Pavement Test Facility (NAPTF) was completed, significant rutting was found to take place in the flexible pavement test sections ’ granular base and subbase layers, designated as P209 base and P154 subbase according to FAA’s construction specifications. To account for the rutting performances of these substantially thick granular layers, a comprehensive set of repeated load triaxial tests were conducted in the laboratory on these P209 base and P154 subbase granular materials. Based on the constant confining pressure (CCP) type laboratory test results, which consider vertical repeated traffic loading directly above a pavement element, mathematical models were developed to predict maximum permanent deformations occurred under both Boeing 777 and 747 gear/wheel loads. A comparison of the measured and predicted permanent deformations indicated that a good match for the measured rut magnitudes could be achieved when the variation of stress states in the granular layers were properly accounted for in the prediction models. The rates at which permanent deformations accumulated in the granular layers with number of load applications, however, could not be fully modeled using the