To evaluate the applicability of three-dimensional ground-penetrating radar (GPR) in assessing interlayer bonding within asphalt pavements featuring semi-rigid base layers, we conducted an analysis of the GPR detection mechanism. Employing forward simulation, various medium models were created to analyze electromagnetic wave transmission in air, water, and sand. GPR testing was applied to four distinct pavement structures, utilizing amplitude intensity levels and image processing techniques to assess asphalt pavement interlayer bonding. The results were validated by comparing them with core samples. The findings revealed a significant influence of medium uniformity on electromagnetic wave transmission processes. Non-uniform media models generate a large number of clutter waves, which refers to amplitudes and phases that have no predictable regularity in time and space i.e., they show irregular ups and downs and fluctuations. It is similar to the clutter that occurs during actual detection. Poorly bonded areas exhibited clearer hyperbolic ripples, primarily attributed to significant differences in the dielectric constants of filling materials. Amplitude strength effectively evaluated bonding across different asphalt pavement configurations and lanes, typically following a normal distribution. Enhanced interlayer contact correlated with smaller amplitudes, while weaker bonding led to larger amplitudes. The amplitude distribution in the center of lanes differed significantly from wheel track areas, indicating better interlayer bonding conditions in the center lanes compared to the wheel track belt. Moreover, radar plan views demonstrated considerable variation across different interlayer contact conditions. The image processing method proved effective in evaluating the interlayer contact condition of various pavement structures across full cross-sections.
