基于地面三维激光扫描技术的隧道全断面变形测量方法

DEVELOPMENT OF A MODELING METHOD FOR MONITORING TUNNEL DEFORMATION BASED ON TERRESTRIAL 3D LASER SCANNING

采用地面三维激光扫描技术测量隧道全断面变形,解决数据采集和数据处理两大方面的问题。数据采集方面,为兼顾数据采集的精度与效率,通过几何分析方法对关键的扫描参数进行优化,给出测站间距和扫描分辨率的最佳取值。讨论隧道内多个测站数据的拼接方法以及不同标靶布设方式对拼接精度的影响,建议采用全局拼接方案以减少误差。数据处理方面,由于地面三维激光扫描的原始数据(称为"点云")不能直观地表示隧道的变形,因此提出基于点云的隧道三维建模算法,使隧道变形可视化。该算法联合采用圆柱面拟合与椭圆拟合进行点云建模,并运用误差分布统计规律进行点云降噪。通过与全站仪的精度比较试验,验证地面三维激光扫描技术在隧道变形测量中的可靠性,利用隧道三维建模算法得到的变形量与全站仪的测量结果相差在2 mm以内。最后,介绍上海西藏路电力隧道以及上海长江西路越江隧道2个工程案例,第一个案例给出单空间隧道中的数据采集和数据处理的全过程及隧道变形结果,第二个案例介绍多空间隧道中的测站及标靶的布设方法。

A new approach is introduced to measure tunnel deformation by means of terrestrial laser scanning （TLS）~ and problems about data collection and data processing are solved. On the one hand, in order to balance accuracy with efficiency during data collection, recommendations about setting distance of adjacent stations and scan resolution are given through geometrical analysis. Besides, approaches to register data collected from different scan stations and the precision of registration are discussed. It is recommended to use global registration method to reduce registration error. One the other hand, since the raw data of TLS called ＂point cloud＂ is unable to display the tunnel deformation explicitly, a new 3D modeling algorithm is proposed so that the tunnel deformation is visualized. The new algorithm combines cylindrical fitting method with elliptical fitting method and reduces noise based on error distribution theory. Using the total station as reference, the reliability of TLS is verified and the difference between total station and TLS is less than 2 mm for tunnel deformation measurement. Finally, two cases of Shanghai Xizang Road cable tunnel and Shanghai West Changjiang Road tunnel are introduced. The first case gives details about data collection and data processing in a single-hole tunnel and shows the results of deformation. The second case focuses on how to set the positions of scan stations and targets in a multi-hole tunnel.