FLEXIBLE PAVEMENT DRAINAGE MONITORING, PERFORMANCE, AND STABILITY

The current study is a continuation of the study FHWA/IN/JTRP Project HPR-2078, "Locating the Drainage Layer for Flexible Pavements." In this previous study, three test sections were constructed in a new pavement on a bypass around Fort Wayne, Indiana. These test sections were instrumented to record temperatures, moisture, frost penetration, rainfall and subdrainage system outflow. Collected data and finite element method (FEM) analysis indicate the subdrainage systems are performing satisfactorily. However, concern developed over the stability and rutting characteristics of the open-graded drainage layers. As a continuation study, longer term environmental and subdrainage performance data were collected. Additional data were collected from falling weight deflectometer (FWD) tests, condition surveys and roughness measurements. Laboratory triaxial tests were also conducted on all asphalt mixtures, unbound aggregate materials and subgrades. Tests of asphalt mixtures were conducted at two loading speeds and both wet and dry. Asphalt mixture tests were conducted at the recorded seven-day high field temperature. These data were used in FEM analysis of the stability and rutting characteristics of the test sections. The three subdrainage systems continue to be effective. There is no change in the ranking of performance. Section 1 (open-graded asphalt drainage layer over a dense asphalt base filter/separator layer) continues to drain significantly faster than sections 2 and 3 (open-graded asphalt drainage layer over a dense aggregate filter/separator layer). Water infiltration through the surface has decreased significantly. The pavement sections are in excellent condition.