Volume 36, Issue 2 (March 2013)
Performance Evaluation of Flexible Pavements Using a New Field Cyclic Plate Load Test
This study presents a new field cyclic plate load test for characterization of the permanent and dynamic deformation behavior of flexible pavements as a function of load and number of loading cycles. Specifically, in this study a Vibroseis was used to apply thousands of loading cycles to pavement sections with a peak dynamic force of 62 kN (a ±22 kN dynamic force superimposed on a static hold-down force of 40 kN), which is approximately equivalent to [3/4] of an ESAL. These vertical loads were applied to a dual wheel-sized loading footprint resting on the pavement surface at a rate of 50 Hz. During loading, the permanent and dynamic surface deformations were recorded every 500 cycles at incremental distances from the loading footprint. The cyclic plate load test was performed for two pavement sections having similar asphalt, subgrade, and base course characteristics, but different base course thicknesses. The results from the pavement sections at two different times of the year (summer and winter) indicate improved performance with increasing base course thickness, and a stiffer response in the winter months due to temperature effects on the asphalt elastic modulus, as expected. The measured permanent deformation basins were interpreted using inverse analysis of an analytical Timoshenko-Winkler beam solution to identify softening of the Young’s moduli of the asphalt and combined base and subgrade layers after application of different numbers of loading cycles. The beam solution provides a good fit to the measured deformation profiles and the inverse analysis shows a clear decrease in Young’s moduli of the pavement layers during cyclic loading.