Shield Tunnel Convergence Diameter Detection Based on Self-Driven Mobile Laser Scanning

Abstract

The convergence diameter of shield tunnels is detected by ellipse fitting or local curve fitting to cross-section points. However, the tunnel section, which is extruded by an external force, has an irregular elliptical shape, and the waist of the tunnel is often blocked by accessories, resulting in data loss. This study proposes a convergence diameter and radial dislocation detection method based on block-level fitting. The proposed method solves the accuracy degradation caused by the model error and point cloud incompletion. First, the noise points in the tunnel section point cloud are removed using the least trimmed squares method. Second, the tunnel transverse seam is then located using the image edge detection algorithm. Third, the endpoint of the convergence diameter is determined by making a specific segment the center and shifting the detector from the center to the pinpoint. Finally, the convergence diameter and radial dislocation are detected by the endpoints of the segments. The experimental results showed that the absolute detection accuracy of this method was better than 3 mm, and the repeated detection accuracy was better than 2 mm. This result is consistent with prior total station measurements, which are more suitable for practical engineering applications.

Resilience of metro tunnel structures: monitoring deformation due to surrounding engineering activities and effect of remediation treatment

“…Recent advances in distributed inspection and monitoring technologies have opened up the possibility to obtain a more refined picture of tunnel deformations. Laser scanning can serve as a promising tool for largescale tunnel deformation inspection, and when aided with suitable software, the retrieval of deformation information could be done in real time [22]. For example, a systematic approach was proposed for tunnel deformation monitoring using terrestrial laser scanning (TLS) [23], in which the point cloud data was registered using the iterative closest point (ICP) algorithm, and the centreline of the tunnel was extracted using a moving least squares (MLS) algorithm.…”

“…Another methodology was proposed for detecting the convergence diameter of shield tunnels using self-driven mobile laser scanning (SDMLS) [22]. A least trimmed squares method was adopted in removing the noise points in the point cloud.…”

Experiment and Application of NATM Tunnel Deformation Monitoring Based on 3D Laser Scanning

“…Based on mobile laser scanning technology, many scholars at home and abroad have designed building information models (BIMs) to develop deformation monitoring systems for tunnels or other retaining structures [10,11]. At the same time, 3D laser scanning technology can not only design the structural positioning and orientation system [12][13][14][15][16][17] but also create a 3D building information model (BIM) [18,19] based on the orientation system. In fact, by optimizing the deformation data extraction and improving the registration algorithm [20][21][22][23], the accuracy of tunnel 3D modeling and deformation monitoring can be efectively improved [14,[24][25][26].…”