ABSTRACT:

To assess whether reinforcement is required for aged tunnel, it is necessary to clarify the rigidity of the concrete lining as well as the distribution of cracks occurred in the lining concrete. Therefore, a “tunnel lining inspection system” was adopted to photograph, extract, draw and quantify the cracks of the tunnel lining automatically. The crack condition was quantified using the fractal dimension. The accuracy of the automatically extracted cracks and the applicability of the health diagnosis system were verified. Meanwhile, the rigidity of the tunnel lining was also evaluated focusing on the vibration characteristics of the lining concrete. The correlation between crack distribution situation, thickness of concrete lining, back cavity etc. and vibration characteristics was discussed. Results show that the Fourier spectrums for tunnel axial direction, the tangential direction, and the three-direction synthesis correlate with the fractal dimension. In addition, it turns out that the Fourier spectrum for the three-direction synthesis may have relevance to the crack fractal dimensions and the lithology around tunnel. It can be judged that the vibration characteristics of the lining concrete is related to not only the crack distribution but also another factors, such as the lithology around tunnel.

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