隧道衬砌空洞积水的探地雷达识别研究

Study of Ground Penetrating Radar Detecting on Tunnel Lining Cavity with Water

衬砌空洞是运营隧道中的常见病害,由于其内部介质复杂,尤其当积水存在时,探地雷达(GPR)识别存在较大难度和误差。针对空洞积水的情况,利用MATLAB编程,建立空洞和不同电导率的空洞积水数值模型,用时域有限差分法(FDTD)进行探地雷达二维正演模拟,通过分析正演图谱和单道波形,得出空洞及积水的响应规律。制作隧道衬砌混凝土模型,应用探地雷达扫描测试,并与正演模拟结果进行对比分析。结果表明,雷达正演与模型试验结果相似;未积水的空洞反射波相位与入射波相反;空洞积水的雷达信号反射更明显,其反射波相位与入射波相同;电磁波在水介质中迅速衰减,空洞积水时,其大小难以定量识别。

Lining cavities are common diseases in operating tunnel. Because of its complex medi- um inside, especially water filling, there are always difficulty and error in ground penetrating radar （GPR） detecting. Firstly, the numerical model of cavity and cavity water with different conductivities is established using MATLAB programming. Then GPR forward simulation is carried out with 2D finite difference time domain （FDTD） method. Through analyzing forward simula- tion map and its single trace, the response character of cavity and water is summed up. Appling GPR on detecting tunnel lining model, comparison is made between the test result and the for- ward simulation one. It is shown that the model test result is similar to FDTD forward simula- tion. The reflected wave phase of cavity is opposite to incidence wave. But phase of cavity water is the same as incidence wave. Furthermore, reflect wave of water is more obvious. Electromag- netic wave attenuation in water is too fast to identify the size of cavity.