注浆材料介电常数在雷达图像识别中的应用

利用探地雷达(GPR)方法探测软土盾构隧道盾尾壁后注浆分布效果时，电磁波在介质中的传播速度是准确识别介质界面的关键。在估计波速时常常将介质的介电常数假设为固定不变的常数，这不符合实际情况。为保证探测图像识别的精度，首次利用网络分析仪对不同配比、不同探测频率和不同龄期下软土隧道壁后注浆材料的介电常数进行了测定，对测定结果进行了基于射线追踪原理的GPR数据二维正演分析，并将分析结果与模拟的探地雷达隧道壁后注浆分布探测结果进行了比较。结果表明，针对不同的探地雷达探测频率而采用相应的介质介电常数来进行探地雷达探测图像的准确识别是十分必要的。

Applications of dielectric permittivity of grouting material to GPR image identification

When we use the ground penetrating radar(GPR) to detect the effect of grouting behind segment at the shield tunnel tail,it is very important to ascertain the velocity of electromagnetic wave(EMW) to obtain accurate results.It is unrealistic to assume that permittivity and electric conductivity are invariable,when the velocity of electromagnetic wave was estimated.In order to assure the precision of GPR image identification,network analytic instrument is firstly introduced to detect the dielectric permittivity of grouting material under the different frequencies,mixture ratios and curing periods.Some direction deduces analyses based on radial tracing theory have been done and compared with the results of the same grouting material on the site.This study shows that it is very necessary to adopt the different dielectric permittivities according to the different frequencies and curing periods.