A Novel FWD Dispersion Curve Method for Pavement Evaluation: Theory, Applications, and Case Studies

Abstract: In-situ modulus is a key mechanical property for pavement design and condition assessment. Traditionally, the modulus of pavement layers is determined using Falling Weight Deflectometer (FWD) testing. Conventional analysis of FWD data primarily involves back-calculating surface deflection based on known layer thicknesses. However, a significant portion of the data generated by FWD tests remains underutilized, representing an untapped resource for comprehensive pavement evaluation. This paper introduces the FWD Dispersion Curve Method, a novel approach that utilizes the full-spectrum FWD data to derive not only the traditional layered moduli but also detailed sub-layer material and structural characteristics, all without requiring prior knowledge of the layer thickness. Previous case studies have demonstrated the feasibility and effectiveness of this method in evaluating the condition of asphalt pavements. It has proven capable of reliably capturing the elastic properties of materials in different layers, estimating layer thickness through changes in modulus gradients, and identifying weaknesses caused by internal layer distresses. Furthermore, we applied this method to analyze the trends in modulus changes across different pavement structural layers under traffic loads, using data from Construction Cycle 9 (CC9) of the National Airport Pavement Test Facility (NAPTF) project by the U.S. Federal Aviation Administration (FAA). These findings could provide strong guidance for analyzing the remaining service life of pavement structures and making informed maintenance decisions.