Permanent Deformations During Traffic Tests on Flexible Pavements at the National Airport Pavement Test Facility

摘要

Measurements of permanent deformations are presented from traffic tests on a stabilized base flexible pavement test item at the Federal Aviation Administration's (FAA) National Airport Pavement Test Facility (NAPTF). The tests were run with four- and six-wheel gear configurations at wheel loads of 20.4 tonnes (45,000 pounds) and over a total wander width of 3.66 m (12 ft). The test item was trafficked to structural failure with permanent deformations at the surface evidenced by rut depths of over 100 mm (4 inches) and upheaval at the sides of the ruts in excess of 25 mm (1 inch). The permanent deformations were measured with three different systems: a 3.66-m (12-ft) straightedge, a rolling inclinometer, and multidepth deflectometers (MDDs). The straightedge results are reported as maximum rut depth at prescribed repetition intervals. The profiler results are reported as transverse profiles at prescribed repetition intervals. And the MDD results are reported as time histories of structure displacements at the surface, in the asphalt layers, and in the aggregate layer. The net accumulated unrecovered (permanent) deformation in the pavement structure over a complete wander cycle is shown to be a small fraction of the range of the unrecovered deformations occurring during the wander cycle over individual back and forth load applications. That is, the sum of the upward and downward unrecovered displacements almost cancel, leaving the structure in approximately the same configuration at the end of a wander cycle as at the start. The unrecovered displacements are about the same magnitude as the recovered (elastic) displacements, with the relative magnitudes depending on the transverse position of the load relative to the transverse position of the measurement. As the pavement test item deteriorated, all three measurement systems showed increased magnitude of the unrecovered displacements. The MDDs also showed increased magnitude of the recovered displacements as the test item deteriorated.