Highway Tunnel Dielectric Constant Study And Application Of The Theory Test

The aim using ground penetrating radar (GPR) to check the quality of the tunnel lining is to grasp timely the thickness, the density and some other circumstances of the tunnel lining in order to conduct the remedy grouting, to take some mending measures and, finally, to reach the goal of controlling the global quality of the tunnel.In this paper, we conduct experiments to simulate the structure of the tunnel concrete lining, and measure the speeds of radar wave through the GPR. Some measurement values of the permittivity of the tunnel lining are then obtained. From experimental results, we find an abnormal phenomenon of the permittivity which shows that the value of permittivity will increase linearly with the depth of the concrete lining. Combining with the characteristics of concrete lining and taking the free water distribution in the concrete lining into account, we propose a volumetric model for the permittivity which can best explain the experimental results. This model can explain the experimental results obtained for the ground penetrating radar used for the tunnel lining concrete lining of the accurate measurement of depth and provide necessary basis for the amendment.As an application of the research results of the above tests and theoretical analysis, we use the American SIR-3000 Ground Penetrating Radar and 900MHz-type antenna to the K3 +760 ~ K4 +360 section of tunnel lining detection in the left hole of Ring Road Sanya, Hainan Yingbin tunnel. Through the compare experiment, we find that there exist some differences between the measure results using the experience value of the dielectric and the measurement results using the revised value of the dielectric. The difference appears not only at the prediction about the cavity and compactness of the lining, but also at the determination of the positions of the quality problems. There is large deviation for the case in which experience value of dielectric is used. While for the case in which revised value of dielectric is used, the derived results are very close to the practical ones, which could be useful guide to the engineering. This situation further indicates that it is necessary for the permittivity value of a lining to be revised according to experimental data. Besides, some places like Sanya in Hainan lying in a tropical climate area receive a heavy annual precipitation, and have comparative high humidity air. As a consequence, the concrete will contain relatively high water content. Therefore, according to our conclusion, it is very important for the experience values of the permittivity of the tunnel lining to be revised, which is in return demonstrate the importance of our study on permittivity of the tunnel lining.Finally, the paper further discusses some research topics of the future.