Thaw Weakening Mitigation of Unpaved Roads in Vermont (05-1779)**
Karen S. Henry, United States Air Force Academy
James P. Olson, University of Vermont
Stephen P. Farrington, Transcendev
Christopher C Benda, Vermont Agency of Transportation
John Lens, GeoDesign Inc.

We evaluated the performance of several techniques thought to mitigate deterioration of unpaved roads during spring thaw. Each potential remedy was aimed at providing some combination of limiting the availability of moisture in the winter, improving drainage during spring and strengthening the upper portion of the road. With one exception, each technique implemented uses locally and/or commercially available materials and all were easy to construct, i.e., a town road crew could build it. Construction was followed by two seasons of monitoring. We compared the percentage of the road covered in ruts and strength estimates based on dynamic cone penetrometer values for treated and control sections. Methods that either 1) permanently improved the strength of the top 12 inches of the road or 2) decreased the water content of the upper 12 inches of the road resulted in significant performance improvement during spring thaw.