Impact of Dynamic Loading on Confined Asphalt Concrete Surface

The behavior of asphalt concrete (AC) is highly dependent on the temperature and frequency of loading. Traditionally, the modulus of AC materials is characterized by performing creep recovery or complex modulus tests without considering the impact of the lateral confinement level. Because traffic-induced loading generates a multi-axial stress state within the pavement structure, quantifying the effect of the lateral confinement on the global AC behavior becomes a necessity. Studies have shown that the responses of dense-graded AC mixtures are highly dependent on confinement levels, especially at low frequencies and high temperatures. In this study, a constitutive model was developed for confinement-dependent linear viscoelastic (LVE) behavior. The model was then incorporated into finite element pavement models using a user material subroutine. The numerical pavement models were used to quantify the impact of lateral confinement on pavement critical responses under various temperature profiles and tire loadings. Multiple loading levels were selected to consider the effect of road roughness on tire loading amplification. Results show that the effect of confinement depends on the relative position of the moving load. Vertical strains under the tire are significantly reduced by confinement. Finally, the maximum percentage decreases in the compressive and vertical shear strains from incorporating the confinement-dependent LVE model were found to be 31% and 17.5%, respectively, for the highest load–temperature combination.