Evaluation of Air-Cavities behind Concrete Tunnel Linings Using GPR Measurements

The primary objectives of this study are to investigate the interference ground penetrating radar (GPR) signals with air-cavities behind concrete linings subjected three experimental parameters (GPR antenna frequency, thickness lining, and air-cavities), their effects on evaluation important engineering (thickness concrete, length air-cavities) for tunnel structure inspection using GPR. For these purposes, first, a model specimen is fabricated in laboratory, which simulates air-cavity defects various thicknesses (0 mm, 30 100 200 300 mm) four different (100 400 structures. Second, series GPR survey performed ground-coupled antennas nominal center frequencies MHz, 900 1600 MHz. Third, practical signal interpretation method proposed evaluate parameters. It demonstrated that cross-correlation analysis effective identifying characterizing air-cavities. In addition, estimated by new approach study, measuring apparent time delay partially overlapped electromagnetic wave reflections within results provide fundamental basis improve techniques linings.