Abstract

In recent years, the Federal Aviation Administration (FAA) Alaskan Region reported performance issues with some flexible airport pavements. The issues were attributed to changes in the thermal regime of the permafrost layers due to a warming trend, but the poor pavement performance could have been exacerbated or caused by factors such as improper design and construction. The FAA Airport Technology Research and Development Branch reviewed the pavement failures, design, and construction histories to determine the cause(s) and contributing factors of flexible pavement performance issues. The goal was to determine if and where modifications to FAA guidance concerning design and construction in frost and permafrost zones were needed.

FAA selected three runways with an asphalt surface and one runway with a gravel surface at four airports in Alaska for detailed evaluation. The airports selected represent a variety of local conditions and permafrost zones. FAA collected design, construction, and traffic documentation from the selected airports. Researchers also conducted interviews with Alaska Department of Transportation and Public Facilities (Alaska DOT&PF) and FAA Alaskan Region engineers involved in the most recent pavement rehabilitation to gain additional insight into the pavement design, particularly with respect to the permafrost condition. The study focused on identifying frost and permafrost issues at the airports, identifying the design criteria used at the airports, and determining how closely the design criteria and construction practices followed FAA guidance. The study also re-created the pavement design for each runway following both the FAA guidance in effect at the time of the design and Advisory Circular 150/5320-6G. Researchers identified areas of the FAA frost and permafrost design criteria that are silent or subject to conflicting interpretation.

The study used findings from the design reviews and provided recommendations for possible improvements to the current FAA guidance with respect to frost and permafrost design. The recommendations targeted Advisory Circulars 150/5320-6G and 150/5370-10H and are intended to address the design- and construction-related issues.