沙堆内小型管线的探地雷达模型实验研究

GPR model experiment for small diameter pipes in sand pile

地质雷达作为一种新的探测技术,广泛应用于城市管线探测、特别是非金属管道(直径Φ为150～400 mm)探测,取得了良好的效果,但是对小口径管道的探测研究不多.本实验是对埋于中等湿度、均匀介质沙堆内的Φ为40～150mm的管线不同组合模型,进行900 M、600 M、200 M雷达反射波图像观测,探讨单管、双管、三管的图像特征,研究探地雷达图像的影响因素.研究结果显示:雷达探测的实际分辨率达不到理论分辨率;高频率天线图像精细,适合探测浅小的管线;管道充填水后,多次波明显增强;路面街砖会削弱雷达的管线异常信号,出现类似倾斜岩层等干扰信号;利用多次反射波可求得管径.本实验有助于我们在城市地下管线探测中能够快速准确地识别各类地下异常体的探地雷达图像.

As a new kind of detecting technology, GPR is widely applied to city pipeline detecting, especially locating nonmetal pipes with diameters from φ150 to 400 mm, and has obtained good results. But there are few studies for pipes smaller than φ120 mm in diameter. Our GPR model test is carried out by 900 M, 600 M, 200 M antenna on the flat surface of sand piles with moderate humidity and homogenous medium where 1 or 2 or 3 pipes （φ 40 to φ150 mm in diameter） are buried, to study the influence factors. The test shows that the actual resolution ability is lower than its theoretic resolution ability. The image of high frequency is detailed and it fits for shallow and small pipeline detecting. Its multiples are evident on radar images if pipeline is filling with water. Street brick will weaken useful radar signal and show pseudo signal with declining layers. The diameter calculation can he made by its multiple reflected waves. It will help us to fast and accurately identify varied abnormal GPR pictures of pipelines from different objects in underground pipeline location projects.