移动式三维激光扫描在轨道交通结构变形监测中的应用

Application of mobile 3D laser scanning in deformation monitoring of rail transit structures

针对轨道交通作业窗口“受限”且传统测量手段无法全面获取隧道状态的问题,本文借助移动式三维激光扫描系统,结合实际工程案例对轨道交通结构进行检测,首先推导了三维激光扫描的基本原理和坐标转换数学模型,通过外业数据采集、内业数据处理获取了隧道点云数据。对比分析临近地铁隧道的深基坑项目施工前后三维激光扫描数据,结果表明:基坑施工过程对隧道结构产生了一定影响,且基坑正对影响区域结构变形最大,外扩影响较小,净空收敛累计变化量最大,为15.4mm。同时使用全站仪对三维激光扫描获取的净空收敛结果进行精度评估,结果证实了:移动式三维激光扫描测量隧道净空收敛和全站仪测量净空收敛累计变化量总体一致性较好,其中83.33%的监测断面累计变化量互差小于2mm。

In response to the problem of“limited”operating windows in rail transit and the inability of traditional measurement methods to fully obtain tunnel status,this article used a mobile three-dimensional(3D)laser scanning system,combined with practical engineering cases,to detect rail transit structures.Firstly,the basic principles of 3D laser scanning and the mathematical model of coordinate conversion were derived.Tunnel point cloud data was obtained through field data collection and indoor data processing.The 3D laser scanning data before and after the construction of the deep foundation pit project near the subway tunnel was compared.The results show that the construction process of the deep foundation pit has a certain impact on the tunnel structure,and the deformation of the structure in the area directly affected by the foundation pit is the largest,while the impact of external expansion is relatively small.The maximum cumulative change in clearance convergence is 15.4 mm.At the same time,the accuracy of the clearance convergence results obtained by 3D laser scanning is evaluated through total station measurement,and the results confirm that the overall consistency between the tunnel clearance convergence measured by mobile 3D laser scanning and the cumulative variation of clearance convergence measured by the total station is good,with 83.33% of the cumulative variation of monitoring sections having a difference of less than 2 mm.