地质雷达在引水隧洞复合式衬砌厚度检测中的应用研究

Study on GPR Detection of Composite Lining Thickness in Headrace Tunnel

针对引水隧洞复合式衬砌厚度的精确检测,以四川某水电站引水隧洞为例,选取了六组典型断面,分析地质雷达剖面图特性,同时对其中一组断面的厚度值进行了定量分析。测试结果表明:围岩岩性、岩层的产状及围岩体的含水率对地质雷达剖面中厚度参数的准确判读有明显影响;衬砌厚度精度判定与衬砌相对介电常数有关,在准确测定衬砌相对介电常数的条件下,能够定量分析复合式衬砌厚度,误差不超过10%;确定衬砌相对介电常数宜取多个标定点的平均值,并宜将地质雷达测试结果同钻孔录像结果进行对比分析。

This paper takes the headrace tunnel of a hydropower station in Sichuan as an example to discuss the accurate detection of the composite lining thickness therein. Six groups of typical section are selected. GPR detection profile features are studied, and quantitative analysis is made on thickness value of cross section for one group. The test results show that surrounding rock lithology, strata attitude and moisture content of rock have obvious impact on accurate interpretation of the thickness in GPR profile. The measurement accuracy of the composite lining thickness relates to the relative dielectric constant of the lining. The composite lining thickness can be quantitatively analyzed provided that the relative dielectric of layer is accurately determined and the error does not exceed 10%. The relative dielectric constant shall take the average number of various gauge points, and the GPR test results shall be compared with drilling video results.