Research On 3D Measurement And Deformation Analysis Of Tunnel Clearance Based On Point Cloud Data

With the rapid development of China’s transportation industry,the construction of various types of transportation infrastructure changes with each passing day.Major projects such as highway and railway extend to the western region.Due to the terrain of the western region,the number of tunnel projects continues to rise.In the process of tunnel construction,tunnel deformation monitoring is an important means to ensure the quality of tunnel construction.With the rapid development of 3D laser scanning technology in recent years,it has the characteristics of fast measurement speed,high accuracy,three-dimensional expression of measured objects,strong anti-interference and so on.It is widely used in practical projects,including bridge engineering,tunnel engineering,slope engineering and so on.Some domestic scholars have applied 3D laser scanner to tunnel engineering,and carried out a series of processing based on tunnel point cloud data,and achieved some results,but did not form a molding product that can be popularized and applied.Therefore,the design and development of tunnel point cloud data processing software can be applied to most tunnels,improve the efficiency of tunnel point cloud data processing,and provide a new and effective way for tunnel engineering monitoring.Based on the point cloud data acquired by 3D laser scanner,AutoCAD platform,Excel data container and VBA language,this paper studies the key technologies of point cloud tunnel central axis extraction,point cloud data coordinate conversion,tunnel continuous section extraction,tunnel section fitting,tunnel over and under excavation discrimination,monitoring point coordinate extraction,monitoring report generation,etc A set of system with the function of data processing of tunnel point cloud is formed,and the applicability and reliability of the system are tested in the actual project.This paper mainly completes the following work:(1)Coordinate conversion moduleThis part mainly uses the improved differential method to fit the tunnel point cloud data to project on the boundary of the designated plane and fit the tunnel central axis to obtain the included angle between the central axis and the corresponding coordinate axis for coordinate conversion,so that the tunnel mileage is roughly parallel to the Y axis,and calculates the azimuth of each point of the section and the central point of the section,and arranges the point cloud data of the section according to the azimuth size Order,which lays the foundation for continuous section extraction and section curve fitting.(2)Section data storage moduleIn this part,VBA is used to establish the relationship between CAD and excel,and the point cloud data transformed by coordinate is used to extract the continuous section at 5m intervals in the direction of Y coordinate axis,and the data of each section is saved in Excel database.All sections or designated sections can be extracted in CAD.(3)Tunnel section analysis moduleThis part extracts the section data saved in Excel database,selects the section point to fit the section curve,obtains the area of the closed graph enclosed by the fitting curve,loads the design section,judges the tunnel over and under excavation condition through coordinate translation,and marks the over and under excavation value of the feature point and the maximum and minimum over and under excavation area.(4)Monitoring report generation moduleIn this part,CAD and excel are developed based on VBA to automatically extract and save the coordinate information of cross-section feature points in CAD;in Excel,the data of each period is summarized,and the observation date is specified to compare with the monitoring data of the previous period to generate the monitoring report.The software has been tested by the tunnel behind the connecting line of Lanzhou New Area of China Lanzhou passenger dedicated line.The accuracy of data processing meets the requirements of deformation monitoring specifications.The system has good stability,low requirements for computer hardware and fast operation speed,which improves the efficiency of data processing of tunnel point cloud.It has a very important application value for tunnel monitoring.