Embedded Coil Sensors to Investigate the Deformation Behavior of Airfield Pavement Unbound Aggregate Base Courses

This paper presents findings from the ongoing Construction Cycle 9 tests at Federal Aviation Administration's (FAA) National Airport Pavement Test Facility (NAPTF) with the objective to investigate full-scale flexible pavement test section performance trends under realistic traffic loading with gear/wheel load wander. Inductive coil sensor technology was adopted to investigate the deformation behavior of unbound aggregate base layers instrumented with arrays of coil sensors installed through the full depth. A dual-wheel tridem-axle (3D) gear configuration applied 58,000-lb (26.3-ton) wheel loads to the test sections with a wander pattern consisting of 66 passes arranged in nine lateral wander positions. Throughout the 26,400 passes applied during the traffic testing, permanent deformation trends with depth were collected and analyzed. The depths at which minimum and maximum deformations took place were determined according to the 3 in. (76 mm) vertical intervals measured by vertical coil pairs. Study findings are quite revealing when analyzing the aggregate base course deformations, in comparison to the overall pavement surface deformations, which could identify damage mechanisms in such thick airfield granular layers and help to evaluate thickness design requirements to effectively protect the subgrade.