SIMULATION TEST OF GPR NON-CONTACT DETECTION ON LINING OF RAILWAY TUNNEL
YANG Yanqing1，HE Shaohui1，QI Falin1，2，JIANG Bo2
(1. School of Civil Engineering，Beijing Jiaotong University，Beijing 100044，China；
2. Institute of Infrastructure Testing，China Academy of Railway Sciences，Beijing 100081，China)
Abstract：The simulation test for the integral lining specimens of railway tunnel by means of non-contact ground penetrating radar(GPR) detection is performed. The influences of different detection distances(the distance from the bottom of GPR antenna to the lining specimen surface) on the image quality and detection accuracy of GPR scans are studied. The test results show that：(1) The non-contact GPR detection on the integral lining can be performed by means of 400 MHz ground-coupled antenna with 10 or 20 cm detection distance. (2) With the increasing detection distance，the image quality of GPR scans decreases，and satisfactory images can be obtained if some measures such as using digital filtering and adjusting gain coefficient on GPR back wave are adopted. GPR image quality and equipment have particular concern，so the appropriate detection distance should be chosen through experiments before detecting in actual projects. (3) In the GPR scans，a variety of preset work conditions can be identified in the experimental design. The location and range of uncompacted backfill，cavity behind the lining，etc. are similar to those obtained when the antenna closes up to the lining specimen surface；and GPR scans can be interpreted qualitatively. (4) The deviation of test results of lining thickness increases with the increasing detection distance. However，apart from a few measuring points having larger deviation，the deviation range of other measuring points is similar to that obtained when the antenna closes up to the lining specimen surface，which can ensure the accuracy of lining thickness. The non-contact detection values after amendment can be consistent with the contact detection values. The deviation ranges of uncompacted backfill and cavity thicknesses behind the lining agree with those when the antenna closes up to the lining specimen surface. The study will be practical value for the development of the vehicle-system GPR detection and the application of non-contact GPR detection technology in actual project.
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2011, Vol. 30 
