A comparative investigation of the pavement layer dielectrics by FDTD modelling and reflection amplitude GPR data

The present work focuses on the application of the Ground-Penetrating Radar (GPR) technique on a flexible pavement structure for the assessment of the layer dielectrics. Two air-coupled GPR systems, with antennas operating at 1 GHz and 2 GHz central frequencies were used for testing and simulation purposes. The effectiveness of the combination of i) the Finite-Difference Time-Domain (FDTD) technique for the simulation of the GPR signal, and ii) the GPR reflection amplitude technique, for the estimation of the dielectrics of the pavement layers, was analyzed. Three steps of processing were proposed and the results compared each to one another. In the first stage, the signal was simulated using design project data for the investigated cross-section and dielectric permittivity values for the (design) construction materials, derived from the literature. In the second stage, the dielectrics were computed by the signal collected within a real-life flexible pavement. Both the two-way travel time and the reflection amplitude techniques were performed. The third step was focused on analyzing the accuracy of the reflection amplitude method combined with the optimized simulation of the GPR signal. The results demonstrated good potential on the use of the proposed approach with respect to the application of the reflection amplitude technique for the assessment of the pavement layer dielectrics.