| Compared with the traditional total station technology,3D laser scanning technology has the characteristics of real-time,automation and high efficiency,and has great advantages in the application of metro tunnel convergence deformation monitoring.This paper mainly analyzes the 3D laser scanning technology from the original point cloud data collection to data processing and optimization,comparative analysis of data results,through MIDAX GTX NX finite element analysis software for tunnel segment internal force and deformation analysis to master its deformation law;Aiming at the problem of scanner accuracy,the error sources are analyzed comprehensively and in detail.The optimization of image blur and small Angle of point cloud data is realized.At the same time,from the perspective of ensuring the safety of subway tunnel operation in an all-round way,the application analysis of tiling map,full section,Angle and wrong platform is carried out.The main research contents and conclusions of this paper are as follows:(1)Combined with the analysis of internal force and deformation of tunnel segments by MIDAX GTX NX finite element software and the characteristic analysis of transverse convergence and deformation of tunnel segments,it can be seen that the axial force,bending moment and Mises stress of tunnel segments are symmetrically distributed on both sides of the segments,and the maximum axial force and bending moment are reached at the top of the segment and at both sides of the standard segment.The Mises stress is maximum at the left or right of the seam between the adjacent block and the standard block.In addition,when the deformation value of the tunnel segment is large,there is a small Angle of opening at the joint of the capping block,the adjacent block,the standard block and the bottom block.When the deformation value of tunnel segments is small,there is a linear relationship between the lateral opening of the joint between the adjacent block and the standard block and the lateral deformation of tunnel segments.(2)There may still be problems in the original point cloud data collected,which is determined by the point cloud data itself.In this case,data optimization processing is needed.Generally,there will be the problem of image blur and small Angle deviation.For the problem of image blur,the speed of the car in the process of data acquisition can be ensured to be stable.For the minor Angle problems of alpha and gama,internal processing software is needed to correct the Angle,and good results have been achieved in this paper through software correction.(3)Through the error analysis of point cloud data,it is found that the left and right deflection of scanner is the main cause of the small Angle deviation of point cloud gray image;By analyzing the accuracy error,it is found that the circular arc method is better fitting for the ring with large central Angle,and the rotation and translation method is better fitting for the ring with small central Angle.In addition,when the thickness of the point cloud section is 4-20cm(excluding the boundary value),the correct and effective ring convergence,ring Angle and ring fault platform values can be obtained.Finally,based on the experimental results of the data of Shanghai Rail transit Line 8 and Line 15,it is obtained that the FARO S70 laser scanner has an average error of 4.24% and the lowest reliability of 93.63% under the mode of 1/8resolution and 3X mass.The accuracy of FARO S70 laser scanner obtained through analysis of large sample data in the mode of resolution 1/8 and mass 3X can provide experience reference for similar projects. |
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