Abstract: Segment misplacement is a common disease that occurs frequently in the whole life cycle of subway shield tunnels. Excessive misalignment may cause huge damages and leakage to the tunnel, which poses a great threat to the durability and safety of the subway tunnel. Existing method uses 3D laser scanning technology to extract cross-sections on both sides of the circumferential seam by determining the position of the circumferential seam for misalignment detection. Unfortunately, existing method still needs to convert the point cloud data into orthophoto images, and then label the image manually. Using such a method is inefficient and the accuracy could be easily affected by the operator. This study proposes a method for detecting circumferential seams of subway shield tunnels based on the featured point cloud of bolt holes. The proposed method make full use of the collected featured point clouds of shield tunnels without generating orthophoto images for detecting the position of circumferential seams accurately and quickly. The authors uses a subway project in Hangzhou as a case study to validate the proposed method. The results show that, compared with the traditional method, the proposed method is highly efficient and satisfies the accuracy requirements of engineering applications.

Key words: mobile 3D laser scanner, shield tunnel, bolt hole, circumferential seam detection, segment misplacement between rings