Tunnel Continuous Cross-section Extraction And Deformation Analysis Using Terrestrial Scanning

With the development of China’s economy rapidly, the tunnel construction scale has led the world. But in the tunnel construction or operational phase, using conventional total station and other measuring tools can not accurately monitor overall deformation of tunnel section. On the one hand it takes a long time for observation, On the other hand it requires a high labor intensity. In order to monitor tunnel deformation safely, effectively and easily, and solve the problem about the tunnel cross section data which is hard to collect, this paper presents a method to extract a continuous section of tunnel based on 3D laser scanning technology and monitoring deformation, this method can be divided into the following four steps: The scanning plan and data collection, the stitching of the points cloud, the local axis fitting, the continuous section extraction and the monitoring deformation. At first, formulate program of scanning tunnel by simulating to scan tunnel, get tunnel point cloud data and complete point cloud data global registration; Then using invariant moments of three-dimensional method to extract tunnel axis; On the basis of tunnel center axis, adjust local tunnel posture, and make the direction of tunnel axis and extracted reference same. Extracting section along the reference direction, then use the second-order method to get the oval section features, Continuous section elliptical characteristics can be used to analyze the convergence of the tunnel; Finally, using the MDP minimum distance projection algorithm analyzes the cross section of the tunnel and the three-dimensional deformation, and determine the convergence or expansion area, and the deformation.In view of the proposed method in this paper, according to the scanning program, using a leica C10 3D laser scanner which the resolution is selected, scanning the tunnel with the distance of 8.14 m, and extracting tunnel section axis at different times, then extract tunnel section continuously, in this paper, through the experiment of extraction of point accuracy within 3 mm, and get a section of the convergence characteristics through continuous elliptical. Then, based on the MDP, the analysis of the section deformation is done, experiments show that the method can determine the convergence or the expansion and get the amount of deformation of their section points, furthermore because of the high resolution in the cross section of the point cloud information, the accuracy of the deformation information is higher. At last, based on MDP, the deformation of 3D tunnel surface is analyzed, and the convergence and expansion region of tunnel section is obtained, and the deformation of its surface is obtained. The experimental results show that the presented method in the aspect of collecting date and extracting tunnel section can meet the precision of the engineering application requirements, can accurately extract the deformation information of the tunnel quickly; At the same time, compared with the traditional way of getting data, 3D laser scanning technology has obvious advantages in number according to the quantity, the speed of data acquisition and manpower requirements.