Abstract:

The cavities behind tunnel lining will cause damage, leakage and other engineering problems. Due to the metal (such as steel and arch frame) in lining, the effect of radar wave will be influenced, which will increase the complexity of radar crosssection and affect the test results. The rectangular cavity and triangle cavity behind tunnel lining is forward simulated by highgrade finite difference time domain (FDTD) method when using 400 MHz antenna and 900 MHz antenna based on MATLAB software platform. The results show that: 1) The propagation characteristics of radar wave in tunnel lining can be simulated accurately by highgrade finite difference time domain method. The reflection of signal of rebar, cavity and shaped steel can be shown and recognized. 2) The 900 MHz antenna can recognize boundary with length of larger than 0.3 m, of which the detection precision is higher than that of 400 MHz antenna and the detection boundary is small than actual one.

Key words: tunnel lining, cavity, ground penetrating radar, highgrade finite difference time domain method, forward modeling