Long-term Monitoring of zigzag-shaped concrete panel in retaining structure using laser scanning and analysis of influencing factors

Retaining structures are required to evaluate their stability not only during construction but also during maintenance. In this paper, the retaining structure was constructed after excavating the slope for the tunnel construction. In order to evaluate the stability of a large-scale retaining structure, laser scanning was applied to monitor the behavior of the retaining structure. Since the retaining structure is composed of zigzag-shaped concrete panels, two scans were performed at six locations to minimize the shadow effect in a zigzag-shaped concrete panel. Various factors such as point cloud comparison methods, distance between structure and scanner, scanning angle, density of point cloud, cloud registration and reference target affect to the comparison of point clouds and hence the influence of these factors on the accuracy of point cloud analysis were determined. Scanning was performed every summer and winter for four years, and the behavior of the retaining structure according to the seasonal effect could be analyzed by comparing the collected point clouds.