Application Of Mobile Laser Scanning In Subway Tunnel Monitoring

In recent years,the urban expansion speed is faster and faster.With the increasing proportion of subway in traffic,the demand for deformation monitoring of subway tunnel structure is more and more strict.With the appearance of 3D laser scanning technology,it is possible to measure the whole tunnel section quickly.However,due to the narrow structure of subway tunnel and the interference of measurement,the fixed 3D laser scanning technology can not be widely used.The mobile laser scanning technology,which combines the track convenience and the three-dimensional laser scanning technology,is born according to the demand.At present,the research on the mobile laser scanning technology in the subway monitoring is very scarce at home and abroad.How to use the characteristics of both,that is,the combination of high efficiency and high precision,has become an important research direction.In view of this,this paper focuses on the mobile laser scanning technology,from the point of view of point cloud,mileage data processing and the actual needs of the project,studies the application of mobile laser scanning technology in subway tunnel deformation monitoring.The main work of this paper is as follows:According to the principle of mobile laser scanning,this paper analyzes the error from the angle of data collection,storage and post-processing.According to the characteristics of odometer data recording,the double odometer model is used to correct the mileage data.Secondly,considering the three-way small angle error between the scanner and the tunnel,it is divided into the forward error of the instrument,the tilt error between the scanner and the tunnel top and the left and right lateral error.These errors will be reflected in the point cloud model one by one,specifically as follows: in the tunnel tiling diagram,the connection joints between the segments will show the phenomenon of distortion and dislocation,which can be based on the image of the circular joints in the tiling diagram For the difference of prime height and width,the scanning line point cloud is corrected.Finally,the convergence calculation of each ring of the tunnel is carried out by adopting the mode of section segmentation.The results of least square fitting of circle,ellipse and polynomial are compared and analyzed,and the ellipse fitting mode and the section segmentation mode with the thickness of 10 mm are determined.In order to verify the feasibility of this method,this paper relies on the monitoring project of Shanghai metro tunnel,carries out the whole process of mobile laser scanning measurement on the adjacent metro tunnel under the influence of the project,and uses the collected data to analyze the application effect in the actual project.At the same time,the whole tunnel of Shanghai Metro Line 13 is measured by mobile laser scanning.The stability and accuracy of the mobile measurement mode are verified by comparing with the long-term convergence data of the same year.