Forward Simulation of GPR Detection for Irregular Concealed Distresses of Road Pavement Based on the FDTD Method

Abstract

Detecting concealed pavement distresses by ground penetrating radar (GPR) has become popular. However, inner distresses develop irregularly, leading to the uncertainty of the feature in B-scan images. Meanwhile, the heterogeneous pavement increases the difficulty of feature determination. To determine the GPR characteristics and their variation rules of irregular features in heterogeneous pavement structures, random multiphase pavement and irregular distress models were established for forward simulation. The parameters such as antenna frequency, distress size, and filling media were set in different values to observe feature variation. Regional average gray-scale value was chosen to characterize the relation between the distress size and reflected wave energy. After forward modeling, the typical B-scan image features of inclined cracks, irregular cracks, irregular debonding areas, and loose areas were identified. The influence of antenna frequency, filling medium, and size of disease on the variation of disease characteristics was also determined. In this study, the reflected wave energy intensity was characterized by the regional average gray-scale value, and the results showed that the size of cracks and debonding areas were positively correlated with the reflected wave energy intensity. The R2 of the vertical air crack, vertical water-bearing crack, and irregular water-bearing crack is 0.977, 0.971, and 0.926, respectively. The R2 of the air debonding area is 0.930.