三维激光扫描技术在滑坡物理模型试验中的应用

大型滑坡物理模型试验中常采用高精度的特征点监测,缺少整体变形资料;而三维激光扫描技术可以高精度、快速、完整地扫描实物,获得海量的点云数据,构建实物的数字化模型,从而详细描述表面细部状况。将三维激光扫描技术引入到滑坡物理模型试验坡体表面整体变形监测中,通过数字仿真试验对点云数据4种变形测量方式进行了对比和评价,推导了点云数据单个扫描点的空间位置精度的评价模型,对点云密度进行了理论分析。通过滑坡物理模型试验实例,采用点云比较、重心法、点云叠加方法测量模型的整体变形和单个监测点的位移,对滑坡不同演化阶段变形特征进行了综合分析。研究表明:空间位置精度的评价模型、点云密度模型为三维激光扫描变形监测的测量成果评定,测量方案的优化设计提供了必要的理论基础。点云叠加、点云比较为面测量,可以获得整个模型坡面的变形和位移情况,测量模型的变形趋势和变形量级,重心法、拟合法则属于点测量,可以获得单个监测点准确的位移量。基于三维激光扫描技术坡面监测是结合点测量和面测量的优势,在保证高精度特征点监测同时,获得模型坡面的整体变形和位移。

Application of 3D laser scanning technology to landslide physical model test

At present, the deformation analysis in the large-scale landslide physical model tests is mainly carried out with point based measurements which are generally more accurate and precise than area based techniques, especially when control targets are used. However, point based measurements provide only information of a few selected monitoring points and not on the whole surface of the model. 3D laser scanning technology captures the integrated, comprehensive, consecutive and associated panoramic coordinate data with a high degree of precision and resolution in extreme speed. It also describes factually the frame and configuration of the object. 3D laser scanning technology has been successfully applied to displacement monitoring and deformation measurement in the large-scale landslide physical model tests. In order to assess the effectiveness of the measurement methods applied to measure displacement in the laser scanning and evaluate their performances, a validation simulation experiment has been carried out. The error evaluation model of the point positional accuracy is derived. The point density in laser scanning is analyzed theoretically; and a practical test stabilized with model piles has been carried out to better understand the mechanics of such type of landslides. The displacement and deformation obtained by cloud to cloud comparison method, the barycenter method and scan data collection at two different epochs are reasoned to describe synthetically the deformation evolution process of the model here. Researches show that: the error evaluation model and point density model provide a theoretical basis for the evaluation of measurement achievement and the optimal designs for the measurement scheme. The cloud to cloud comparison method and scanning data collection techniques are area based measurements, while barycenter method and the benchmark method are point based. With point based measurement small deformations can be detected in only a few selected positions due to the largely manual measurement process. The area based methods give a good approximation of the displacement amplitudes and provide the whole deformation of the slope surface. The application of the 3D laser scanning technology to the landslide model test has the advantage of combining both the point based and area based methods. It provides the whole deformation while maintaining the high precision for the selected positions.