The influence of layer interaction models and horizontal loads on flexible pavement strain responses

This study investigates the influence of interlayer bonding conditions and horizontal loading on the mechanistic response of flexible pavements using Finite Element (FE) analysis. A spectrum of interface models – frictionless, simple friction, and full bond – was analyzed, and the resulting pavement strains were benchmarked against the perpetual pavement criteria established by the National Center for Asphalt Technology (NCAT). The results indicate that subgrade rutting is the dominant failure mode, with vertical compressive strains exceeding the 200 µε NCAT threshold in most realistic bonded scenarios. A critical finding is the distinct impact of the analyzed parameters on different failure modes: horizontal loads were found to significantly increase tensile strains in the asphalt layer (fatigue risk) but had a negligible effect on compressive strains at the subgrade level (rutting risk). These findings highlight the necessity of including horizontal loads in fatigue analysis and demonstrate that the simple friction model provides a realistic intermediate condition between the idealized performance boundaries of the full bond and frictionless states. The study concludes by recommending further research to calibrate practical interface parameters to enhance the accuracy of pavement performance predictions.