Integrated monitoring method and software for shield tunnel profiles by 3D laser scanning technology

During shield tunneling, inaccurate measurements and delayed corrections can lead to deviations of the propulsion axis from the design alignment. Therefore, timely monitoring and measurement of tunnel sections after the assembly of shield construction tube segments are essential. While 3D laser scanning technology provides significant potential for tunnel section monitoring, extracting tunnel profiles in curved tunnels remains challenging, and software dedicated to post-processing point cloud data for shield tunnel profiles is limited. This paper presents an integrated method and software system for monitoring shield tunnel cross sections, including curved alignments, using 3D laser scanning data. The approach employs a vector-based extraction method that uses design data to calculate section normal vectors, avoiding reliance on central axis fitting from point clouds in curved segments. The workflow, from data acquisition to deformation visualization, is implemented within a dedicated software tool, providing a practical solution for shield tunnel profile post-processing.