A dynamic load test study was performed on instrumented asphalt and concrete pavement test sections at the Minnesota Road Research facility. Test variables included different types of vehicles (featuring various axle groupings, load levels, and tire pressures) operating at various speeds over different structural sections. Four flexible pavement sections were selected for inclusion, and the primary structural response measured was horizontal strain at the bottom of the asphalt layer. The test data suggest that the structural response of the four sections to varying loads was linear when other test parameters were held constant. The pavement sections also exhibited a pronounced viscoelastic behavior in response to changes in vehicle speed and load rate. This behavior was attributed mainly to the asphalt concrete layer. Changes in tire pressure did not significantly affect pavement behavior. The test data were used to validate a multilayer linear elastic pavement structural model. Subgrade and base moduli inputs were backcalculated from falling weight deflectometer data, and the asphalt modulus was determined experimentally from measured strain. This model adequately reproduced the strain distribution observed at the bottom of the asphalt layer under the passage of moving vehicles with certain limitations: the longitudinal strain asymmetry due to viscoelastic effects could not be reproduced, and the modulus of the asphalt layer had to be readjusted for temperature and vehicle speed. Also, it was not possible to calibrate or fit the model to observed longitudinal and transverse strains simultaneously because the pavement behaved more stiffly longitudinally than transversely.
Abstract