High-Resolution Dual-Frequency GPR for Non-Destructive Detection and Characterization of Subsurface Voids in Pavement Structures

Abstract Ground-penetrating radar (GPR) is a rapid, non-destructive geophysical technique widely used for subsurface defect detection beneath road pavements. However, conventional single-frequency GPR systems face inherent trade-offs between penetration depth and resolution. To overcome these limitations, this study proposes a novel dual-frequency GPR approach for comprehensive subsurface assessment. Numerical simulations were performed to model the electromagnetic responses of typical road defects, such as voids and loose zones, and to establish their characteristic radar signatures. These simulations provide a theoretical framework for interpreting real-world GPR data with higher accuracy. Field validation was conducted using dual-frequency GPR data collected from a road section in Guangxi Province, China. The results demonstrate that high-frequency GPR signals (e.g., 1.6 GHz) achieve superior resolution for shallow defects (<3 m depth), enabling precise delineation of thin layers and small-scale anomalies. In contrast, low-frequency signals (e.g., 400 MHz) exhibit enhanced signal-to-noise ratios (SNR) and improved detection capabilities for deeper defects (>3 m). By synergistically integrating both frequencies, the proposed system optimizes the balance between depth penetration and vertical resolution, facilitating reliable identification of defect types, spatial distribution, burial depths, and lateral extents. This methodology offers a practical and efficient solution for urban road subsurface hazard detection, supporting proactive infrastructure maintenance and risk mitigation strategies.