Extraction of assembly quality information in shield tunnels from LiDAR data

This study presents an efficient method for extracting assembly quality information from shield tunnels using Light Detection and Ranging (LiDAR) data. This method comprises four crucial stages: (1) axis extraction and coordinate conversion, (2) circumferential seam detection, (3) longitudinal seam identification, and (4) dislocation and ovality calculations. To validate the proposed method, a case study of a tunnel in Guangzhou was conducted. The results demonstrate the effectiveness of the method for extracting longitudinal seam locations, dislocations, and ovality information. This method can extract the dislocation and ovality for all rings of the shield, allowing a direct comparison with allowable values to identify locations. The results show that most dislocations in the tunnel meet the specification requirements, with only 6 rings exceeding 17 mm and 9 rings having an ovality above the 6 ‰ limit, as extracted from point cloud data. Compared with existing measurement methods, this method captures a more comprehensive range of deformation information for the entire tunnel, providing essential insights for engineering management. Furthermore, a comparison with current point-cloud processing methods shows that the proposed method processes global point cloud data with a higher accuracy.