ROADWAY BASE AND SUBGRADE GEOCOMPOSITE DRAINAGE LAYERS

The Maine Department of Transportation (DOT) in conjunction with the University of Maine and the U.S. Army Cold Regions Research laboratory evaluated the use of a special geocomposite drainage net as a drainage layer and capillary barrier (to mitigate frost heave) on a section of road plagued with weak, frost-susceptible subgrade soils and poor pavement performance. The special geocomposite drainage net that is being used has a higher flow capacity than conventional geonets and, based on tests performed by the University of Illinois, does not deform significantly under heavy traffic loading. For the 425-m-long test section, the geonet drainage geocomposite was placed horizontally across the entire roadway but varied in vertical location to form three separate subsections for evaluating drainage of (1) the base coarse aggregate, (2) the asphaltic concrete pavement, and (3) the subgrade to allow for a capillary break in order to reduce frost action. An integral drainage collection system was installed to collect the water flowing in the geonet. This paper includes a project description, material and construction specifications, installation procedures, instrumentation, and test results based upon two seasons of monitoring. Laboratory characterization and performance testing initially used to evaluate the geocomposite are compared with the monitored results.