| As an efficient and advanced non-destructive detection approach, GPR can scan the lining of tunnels successively, thus obtaining objective and accurate plots. The use of ground penetrating radar (GPR) has become widespread in highway tunnel inspection. However, the application of this radar has just commenced in China, accompanied with many problems, such as the setting of preferences, the judging principles of the probing plots, and analysis of collected data, which affects the reliability of the results probed by this kind of radars.The paper based on the development and its character of FDTD, mainly discussed its character: turned the differential coefficient to discrete one, and built YEE grids in the variable space, started at double Maxwell spinning equations, exported time-domain limit difference equation of TM wave in the two-dimension space, used PML boundary condition for the simulation of electromagnetic wave in infinite space, solved the strong reflection in truncation boundary of grid space. The paper compiled a forward numerical simulation program using MATLAB 6.5 software, it can simulate all kinds of medium models, through the forward simulation of lots of medium model which usually detected in tunnel linings, and got better result, and it provided a contrasting object for latter work in the paper.The paper did research on the thickness, depth, different spacing steel, and other bugs in the second concrete lining, through the model experiment of GPR in the highway tunnel lining detection. After comprehensive analysis of experimental data and graphs, the author found out that the effect of detection related to the space between bugs and steel, sliding section, covering depth of bugs and dielectric constant.
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