采用探地雷达探测隧道二衬异常的过程中,很多因素会对探测效果产生影响,如发射和接收天线的连线与探测方向间不可避免会呈不同夹角,从而形成不同极化波。主要针对不同夹角α这一因素对隧道二衬探测效果的影响展开研究。为消除这一影响,指导实际施工和信号解释,通过GprMax3D加载线极化中不同天线极化方式建立不同环境的隧道二衬异常模型。由模型模拟分析和工程实例研究发现当夹角α由0°至90°变化时:①对于隧道二衬不同埋深钢筋,采用天线水平极化探测效果逐渐减弱,采用天线垂直极化探测效果基本保持不变;②对于隧道二衬空洞,采用天线水平极化探测效果逐渐减弱,采用天线垂直极化探测效果基本保持不变;③对于隧道二衬混凝土厚度不足区,采用天线水平极化探测效果越来越明显,采用天线垂直极化探测效果越来越弱;④对于隧道二衬破碎带区,无论何种极化波,对破碎带区的探测效果均影响不大,而更多的是受围岩综合介电常数值的影响。研究结果为隧道施工过程中二衬的质量检查提供了指导方法。

The detection of anomalies in the secondary lining of tunnel using ground penetrating radar (GPR) is affected by many factors, such as the difference of linear polarization mode caused by varying angle between the antenna connection and the detection direction. Analyzing the modes of linear polarization would offer guidance for construction and signal interpreting in detecting the defects of tunnel’s secondary lining using GPR. In this paper, the detection effects corresponding to horizontal polarization and vertical polarization are examined by establishing numerical models via GprMax3D. Numerical simulation and engineering example analysis reveal that with the angle varying from 0° to 90°, 1) the effectiveness of detecting steel bars in different depths in horizontal polarization mode attenuates gradually, while the effectiveness with vertical polarization remains unchanged; 2) the effect of detecting cavities of the secondary lining in horizontal polarization mode also diminishes gradually, whereas the effect with vertical polarization stays stable; 3) on the contrary, the detection of thickness-insufficient zone in horizontal polarization mode strengthens, but in vertical polarization mode the detection effect weakens; 4) the detection of crushed zone is barely affected by polarization mode but by the value of dielectric constant of surrounding rock. The above research findings can be used to guide the quality inspection for the secondary lining of tunnels.