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. 2019 Oct 2;19(19):4278.
doi: 10.3390/s19194278.

Rapid Acquisition and Identification of Structural Defects of Metro Tunnel

Qing Ai  1 , Yong Yuan  2   3
Affiliations

Rapid Acquisition and Identification of Structural Defects of Metro Tunnel

Qing Ai et al. Sensors (Basel). .

Abstract

Metro systems in urban cities demand rapid inspection methods, in order to identify critical structural defects in a timely manner. However, traditional inspection methods are only specific to one kind of structural defect, which reduces the overall efficiency of inspection. This study proposes an integrated solution for rapidly acquiring and identifying two kinds of structural defects (surface defects and cross-sectional deformation) in a metro tunnel, using a cart equipped with non-metric cameras. The integrity and rapidity are considered in formulating a systematic design for the development of the acquisition device. Methodologies based on image processing and photogrammetry are proposed to identify the structural defects of the metro tunnel. A series of on-site tests validate that the proposed method has enough speed and has acceptable accuracy in detecting critical structural defects of metro tunnels. The cost and efficiency analysis shows that the proposed method is competitive, which will greatly improve the efficiency and reduce the costs of the inspection of metro tunnels.

Keywords: image processing; inspection method; metro tunnel; photogrammetry; structural defects.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
The design of obtaining surface defects and the cross-sectional profile, from the aspect of integrity.
Figure 2
Figure 2
Integrated acquisition during inspection: (a) Mode of acquiring surface images and (b) mode of acquiring profile images.
Figure 3
Figure 3
Surface defects in a metro tunnel: (a) Leakage, (b) Spalling and (c) Crack.
Figure 4
Figure 4
Image differencing strategy.
Figure 5
Figure 5
Connected regions in an image.
Figure 6
Figure 6
Transmissive projection of tunnel profile.
Figure 7
Figure 7
Bilinear interpolation method for calibrating image distortion.
Figure 8
Figure 8
Calibration of transformation matrix between cameras.
Figure 9
Figure 9
Calibration of relationship between the camera and the tunnel profile.
Figure 10
Figure 10
Assembling the device during the on-site application.
Figure 11
Figure 11
Extraction of man-made leakage in the metro tunnel.
Figure 12
Figure 12
Identification and validation of real leakages in the metro tunnel.
Figure 13
Figure 13
Areas of identified leakages in the metro tunnel.
Figure 14
Figure 14
Identified cross-sectional profile of metro tunnel: (a) By the proposed method and (b) by the total station.
Figure 15
Figure 15
The assumed cross-sectional profile of a deformed metro tunnel.
Figure 16
Figure 16
Identified cross-sectional deformation in metro tunnel.
Figure 17
Figure 17
Discrepancy of cross-sectional deformation close to a cross-passage of the metro tunnel.
Figure 18
Figure 18
Comparison between the proposed method and the total station.
See this image and copyright information in PMC

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