Research On The Detection Technology Of Tunnel Lining Based On The Respones Characteristics To Electromagnetic Wave

In the tunnel construction process, due to the complex geological conditions, badconstruction environment, construction technology and other factors, as can easily cause baddisease to tunnel lining such as holes, cavity and less dense. Therefore, to strengthen thetunnel lining anomaly response feature recognition has important significance to correctlyinterpreter the detection spectrum of the tunnel lining and improve the reliability of detectionresults。Firstly， according to the theory of electromagnetic field, researched the propagationcharacteristics of electromagnetic waves in lossy medium and multilayer medium. Throughthe analysis the echo signal of small target in the B-scanl, verified the propagationcharacteristics of a hyperbola of GPR echo signal of the small target. Secondly, by use of theelectric difference between the target and environment detecting, applying finite differencetime domain method (FDTD) forward simulated the hole which the lining inner transversediameter changes, analyzed the influence on electromagnetic wave reflection responsecharacteristics of hollow transverse diameter change. The results show that: with the increaseof transverse diameter of hole, forward synthetic spectrum changes from hyperbolic graduallyto the rectangular. It provides supports to correctly identify the defect spectrum feature oftunnel lining cavity. Thirdly, by designing a cylindrical concrete model with a rectangularhole and circular aperture hole in the wall，tested the reflex response characteristics of groundpenetrating radar to the holes，funded the reflex response characteristics to the holes arehyperbolic. It is fit for the results of forward simulating. As provide effective support for therecognition of radar spectrum, improve the reliability for subsequent interpretation.Finally, based on sufficiently understanding the propagation characteristics of GPRelectromagnetic waves in lossy media, multilayer media as well as the correctly identifyinglining cavity, by the support of forward simulation and physical model test, applied theground penetrating radar to tunnel lining and the second lining layer thickness detection inone tunnel, completed the interpretation of the four main structural defect spectrum such asless dense, holes, continuous void and triangle void, improved the reliability of GPR in thedetection in tunnel lining.