Difference Analysis Method For 3D Laser Scanning Point Cloud Of Railway Tunnel And Its Application

Tunnel monitoring is the use of special instruments and methods to monitor the tunnel deformation phenomenon,and then analyze the collected data to determine the location and size of the tunnel deformation.The data collected by traditional deformation monitoring methods are too discrete and sparse.The three-dimensional laser scanning technology uses a non-contact high-speed laser measurement method,which has the advantages of high measurement accuracy,fast speed and high density,and can completely display the three-dimensional structure of the tunnel inner wall.How to make a difference analysis of the point cloud of any shape railway tunnel to obtain the location and size of the tunnel change is the core problem of this paper.Based on the existing analysis methods of cross-section difference based on tunnel point cloud,combined with the complex and changeable section of railway tunnel,but the basic design elements in different tunnel cross-section are only one or two of the characteristics of arc and straight line section,Analytical method of cross-section difference suitable for point cloud of any shape railway tunnel.Firstly,a unified design model for railway tunnels with different cross-section shapes,such as horseshoe,round arch,straight wall,and circle,is proposed.Then,according to the topological relationship between the tunnel cross-section and the design cross-section,the algorithm for determining the correspondence between the tunnel cross-section and the design element is proposed.Based on this,a cross-section difference analysis based on the projection of the cross-section profile of the tunnel design is realized.Solved the problem of analyzing the cross-section difference of point cloud of any shape railway tunnel.Through multiple sets of simulation experiments,it is verified that the method in this paper has higher accuracy than the traditional cross-sectional difference analysis method based on circular projection.A plane expression image method based on the analysis results of the point cloud difference analysis of railway tunnels is proposed.A projection method based on the contour line of the tunnel design is proposed to realize the complete expansion of the point cloud on the inner wall of the tunnel into a grid-shaped color image without dead angle and deformation.It can express the actual mileage of the tunnel,the length of the horizontal tunnel inner wall,and the difference between the tunnel inner wall and the tunnel design model.Solved the problems of 3D tunnel point cloud expression differences,although intuitive,but need to change the angle to fully view,and the traditional method based on cross-section expression difference lacks information between cross-sections and other issues,which can fully reflect the difference between the inner wall of the tunnel and the design,the spatial distribution,shape and degree of.The research results of this paper were applied through the Jishou tunnel with a length of 12.162 km on the Zhangjihuai high-speed railway.The over-under-excavation of the tunnel excavation surface,the pre-analysis of the thickness of the second liner of the tunnel,the analysis of the completion of the thickness of the second liner,the volume of concrete filling,and the completion of the second liner,The clearance and other aspects were tested,and after the on-site verification of the project,the accuracy of the results of the cross-section difference analysis method can meet the construction requirements of the project.