Abstract
The use of terrestrial laser scanning (TLS) point clouds for tunnel deformation measurement has elicited much interest. However, general methods of point-cloud processing in tunnels are still under investigation, given the high accuracy and efficiency requirements in this area. This study discusses a systematic method of analyzing tunnel deformation. Point clouds from different stations need to be registered rapidly and with high accuracy before point-cloud processing. An orientation method of TLS in tunnels that uses a positioning base made in the laboratory is proposed for fast point-cloud registration. The calibration methods of the positioning base are demonstrated herein. In addition, an improved moving least-squares method is proposed as a way to reconstruct the centerline of a tunnel from unorganized point clouds. Then, the normal planes of the centerline are calculated and are used to serve as the reference plane for point-cloud projection. The convergence of the tunnel cross-section is analyzed, based on each point cloud slice, to determine the safety status of the tunnel. Furthermore, the results of the deformation analysis of a particular shield tunnel site are briefly discussed.
Highlights
Tunnel construction has boomed in several metropolises because the inclusion of a tunnel makes traffic movement efficient and convenient
The present study aims to develop a systematic method for tunnel deformation monitoring with accurate point-cloud data
terrestrial laser scanning (TLS) has been widely utilized in engineering surveying projects, wider application in the fields of deformation monitoring, especially in the tunnel-monitoring arena, still faces many obstacles, such as extensive metadata processing and low-accuracy data analysis
Summary
Tunnel construction has boomed in several metropolises because the inclusion of a tunnel makes traffic movement efficient and convenient. The detailed and accurate measurement of tunnel elements with conventional instruments is generally unavailable Another existing tunnel deformation monitoring method is based. The present study aims to develop a systematic method for tunnel deformation monitoring with accurate point-cloud data. An orientation method of TLS (OMTLS) is proposed for point-cloud registration from different scan stations At this stage, a positioning base (PB) is designed for the precise orientation of the terrestrial laser scanner to the reference coordinate. The moving least-squares (MLS) method is adopted to thin the scattered point clouds and obtain the centerline of the tunnel from the point clouds In this process, the point clouds acquired from TLS are projected onto an appropriate plane and converted to a planar image for data compression and extraction.
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