In order to accurately monitor the cross-sectional deformation of an underwater tunnel of a reservoir without damaging its structure, research has been conducted on the application of non-destructive testing technology in the measurement of underwater tunnels in reservoirs. A three-dimensional laser scanner is employed to acquire point cloud data from the underwater tunnel. Subsequently, this data, along with control point data, is imported into the Leica Cyclone software. After performing relative coordinate stitching and absolute coordinate stitching, statistical filtering is applied to remove large-scale noise points that are far from the main body of the point cloud. By extracting curvature geometric features, noise points near the main body of the point cloud are filtered out. After determining the central axis of the tunnel using an ellipse-fitting-based central axis extraction method, the cross-sections of the underwater tunnel are fitted and extracted with this central axis as the reference. Then, through the model subtraction method for overall deformation analysis, multi-period encapsulated surfaces of the tunnel are constructed. By comparing these surfaces, deformation measurement of the cross-sections of the underwater tunnel is achieved. The experimental results indicate that this technology can effectively filter out outlier noise and noise near the main body while preserving the features of the main point cloud. The extraction results for the central axis of the tunnel, as well as the major and minor semi-axes of the cross-sections, show small errors compared with actual measurements obtained using a total station. The maximum error for the major and minor semi-axes does not exceed 1 mm and the minimum error is only around 0.3 mm. This technology enables precise monitoring of tunnel deformation.
Wang et al. (Wed,) studied this question.
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