Automated Pavement Thickness Evaluation for FWD Backcalculation

Knowledge of the bound pavement layer thickness is important in obtaining accurate back-calculated layer moduli, since small deviations between assumed and actual layer thickness produce large differences in back-calculated moduli. This paper describes the development and application of a fully automated system for analyzing the GPR data. The system searches out the FWD analysis location in GPR thickness data, identifies the significant layers, chooses the layer boundary that most likely represents the bottom of the bound material, and reports the depth to this boundary. The user can plot these bound layer thickness results for a series of FWD tests, check consistency in the selected layer structure, and, where indicated, select alternate layer thickness choices for those locations that appear to be out of pattern. The paper describes the methodology employed in this system, and the results of the evaluations that have been carried out to date.