Research On The Application Of 3D Laser Scanning Technology In Subway Tunnel Monitoring

Because of the particularity of underground construction,it has become very important work to monitor and analyze the safety and stability of subway tunnel.With the continuous updating of surveying and mapping technology,the monitoring instruments and methods of subway tunnel have also changed,from the traditional methods to 3D laser scanner,from the single-point precision to comprehensive efficient monitoring object surface.Due to the characteristics of non-contact,efficiently,automatically and quickly obtain high-quality 3D mass point cloud data,the application of 3D laser scanner in subway tunnel deformation monitoring projects and researches is increasing.Firstly,introducing the research status and the working principle of 3D laser scanner in tunnel monitoring,the characteristics and accuracy and preprocessing methods of point cloud data,and the source of error.Taking a subway tunnel in Kunming as an example,a mobile 3D laser scanner was used to collect the complete phases three point cloud data of inside a subway tunnel and analyzed the deformation of the tunnel through data processing.Compared with the traditional operation,the operation efficiency of the external and internal industries are greatly improved.According to the structural characteristics of subway tunnel,the transformation of point cloud coordinates under relative measurement mode,the extraction of tunnel cross section and the denoising and fitting of section are described.With the help of original parameters,the deformation of subway tunnel is analyzed from four aspects: radial convergence of tunnel,over-under excavation,ellipticity and segment staggered platform.The results are as follows: Due to the influence of the upper pressure,the tunnel has convergent deformation in the horizontal and vertical direction;The cross-section ellipticity of the three monitoring data at different odometers in the public interval does not change much,and the overall deformation is relatively stable.There are 13 segments staggered in the public monitoring interval,with average staggered platform value is 21.5mm.The accuracy of point cloud data processing can reach mm level,and the overall deformation of tunnel section is small and stable.The results show that the method of collecting tunnel point cloud data by mobile 3D laser scanner is efficient and convenient.Compared with traditional operation,the data processing process is simpler and clearer,and the application value and accuracy of tunnel point cloud data are higher.