Factors Affecting Laboratory Rutting Evaluation of Airport Pavement Granular Layers

This paper presents research findings on characterizing and predicting the permanent deformation behavior of airport pavement granular base/subbase layers constructed and tested at the National Airport Pavement Test Facility (NAPTF) in the United States. The P209/P154 aggregate materials were used in the construction and testing of the NAPTF flexible pavement test sections with variable thickness base and subbase courses. 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 the P209 base and P154 subbase granular materials. Based on the laboratory test results, mathematical models were developed to predict maximum permanent deformations occurred under both 6-wheel and 4-wheel gear loadings applied following a wander pattern. The performances of the developed rutting models were evaluated for predicting the field accumulation of permanent deformations by properly taking into account the NAPTF trafficking data and the previous loading stress history effects. A comparison of the measured and predicted permanent deformations indicated that a good match for the measured rut magnitudes and the accumulation rates could be achieved only when the magnitudes and variations of stress states in the granular layers, number of load applications, gear load wander patterns, previous loading stress history effects, and trafficking speed or loading rate effects were properly accounted for in the laboratory testing and permanent deformation model development.