Asphalt pavement modulus backcalculation using surface deflections under moving loads

The measurement of pavement surface deflections under moving loads can be used for evaluation of pavement structural condition. The objective of this paper is to develop an innovative backcalculation method to calculate pavement layer moduli based on traffic speed deflectometer (TSD) measurements and analyze factors influencing backcalculation results. The backcalculation method is based on 2.5D finite element method (FEM) and constrained extended Kalman filter (CEKF). Field measurements at different pavement sections were used to verify the accuracy of backcalculation results. Parametric analysis was conducted to evaluate the influences of traffic loading and pavement structure variations in the field. It was found that the backcalculation results were considerably affected by the variation of asphalt layer thickness and dynamic loading due to pavement surface roughness. A heavy truck passing the adjacent lane during TSD testing could also cause variation of backcalculation results.