Dynamic backcalculation of asphalt pavement layer properties using spectral element method

Abstract

The response analysis mode of asphalt pavement plays a critical role in properly interpreting falling weight deflectometer (FWD) test results and obtaining reasonable backcalculated layer properties. This study uses the spectral element method (SEM) to analyse the dynamic viscoelastic response of asphalt pavement subjected to FWD loading. The modified Havriliak–Negami (MHN) mode is used to characterise the mechanical properties of asphalt concrete (AC). The MHN model can accurately characterise the viscoelastic and damping behaviour of AC with much fewer number of model coefficients (only five) than the widely used Prony series representation, which makes the model well suited for the dynamic response analysis and backcalculation of layer properties. A computer code is developed to implement the SEM procedure and the results are in good agreement with finite element analysis. The dynamic and quasi-static viscoelastic responses are compared and the results show that the inertia and damping behaviour greatly influences the surface deflection of asphalt pavement under FWD loading, especially for pavements with cemented treated base. Therefore, it is important to consider the dynamic effects in interpreting FWD data. The SEM method is used as the forward analysis engine to backcalculate field FWD data, and the results show that the proposed approach is able to well simulate the deflection history at the pavement surface. The layer properties backcalculated from dynamic viscoelastic analysis are significantly different from those obtained from the traditional backcalculation procedure based on the layered elastic theory.