Comparison of design thicknesses for flexible airfield pavement based on agency limiting subgrade strain criteria

A newly developed mechanistically based design procedure for airfield hot-mix asphalt pavement is studied. The pavement performance is calculated in terms of critical strains on the basis of multilayer theory. Rutting failure criteria from the Asphalt Institute, Shell Oil, and the revised U.S. Army Engineer Waterways Experiment Station (USACE-WES) are used to calculate the thickness requirements necessary for a range of design input variables. The program has been implemented in ZAPRAM, an event-driven, user-friendly educational computer program that runs in the Excel 2007 environment, coupled with Visual Basic programming. Results of the design comparison indicate a significant difference between the three common airfield pavement design procedures used. Differences between the Asphalt Institute procedure and the revised USACE-WES procedure are relatively moderate for all design situations. The greatest deviation is found between the Shell Oil approach and the other two criteria. The design difference depends heavily on several major factors. An analysis of heavy aircraft (B-747) operating on a low-support subgrade foundation may yield pavement design differences of 2 to 3 ft of granular subbase material. A major effort to enhance the state of the art for airfield pavement design models is recommended.