It is theoretically proved that the influence of model boundary the ground penetrating radar(GPR) data acquisition; and based on the theory

designing the physical model within the empty of tunnel lining

probing the model with 3D detection

then the visualization of 3D GPR detection data is realized. We analyze the features of the square hole in the different sections

based on the analysis of CL4 multi-wavelet theory

discuss the necessity of the multi-wavelet preprocessing

and process the CL4 multi-wavelet with balance

using Matlab to realize the CL4 balanced multi-wavelet threshold filtering algorithm; and comparing with the filtering effect based on the conventional Fourier transform. The results show that the 3D detection can determine the size and shape

also including location of the hole

understand the accurate information of hole comprehensive and meticulous

improve the reliability and accuracy of the analyses on radar map

evaluating the harm of hole in lining according to the size and location of defect. The conventional and CL4 multi-wavelet filter can distinguish the unusual target exactly; the target feature has been enhanced with the multi- wavelet transfer

therefore

it results to the cleaner phase axis

more thoroughly eliminate-noise

the same to signal reservation becomes more completely; and the picture also becomes more clearly. The implementation of 3D detection test for the tunnel lining automatic identification technology not only provides a reliable theoretical basis and method

but also has great significance to tunnel detection and quality judicatory appraisal