基于无人机LiDAR的榆神矿区采煤沉陷建模方法改进

Improvement of mining subsidence modeling method based on UAV LiDAR in Yushen mining area

  • 摘要: 煤矿地表沉陷监测中常规的大地测量和InSAR等遥感手段均有一定的局限性。利用无人机LiDAR对沉陷区进行地面扫描,通过多期数据叠加可快速获取地表沉陷盆地的精细特征。然而,按现有的主流点云滤波及插值算法所构建的沉陷模型往往包含显著噪声,限制了该技术在矿区的实际应用。以榆神矿区某开采工作面地表为实验区,针对其地形起伏而植被覆盖度较低的地理环境,利用低空无人机LiDAR获取两期4组地面点云数据,结合常规地表移动实测数据,研究基于激光点云的矿区沉陷建模改进方法。分别采用专业化数字高程模型插值、反距离权重插值、克里金插值、自然邻域插值、样条函数插值及三角网渐进加密滤波、基于高程阈值的滤波、多尺度曲率滤波、基于坡度阈值的滤波、渐进形态学滤波等主流点云插值和滤波算法,构建实验区数字高程模型(DEM)并进行误差对比分析,发现专业化数字高程模型插值及三角网渐进加密滤波算法的效果相对较优,但两期DEM叠加生成的初始沉陷模型仍然精度不足,主要包含点云平面位置误差、非地面点噪声、点云内插误差、水域覆盖范围变化等引起的模型误差。在分析上述误差分布特征及其改进途径的基础上,提出基于小波阈值的沉陷模型去噪优化方案。针对沉陷盆地和非沉陷区域选用不同的小波参数,先利用非沉陷区下沉值为零的先验条件,对全区域数据进行多层次小波分解,再对沉陷区进行低层次小波分解,最后将两者结果进行镶嵌处理。实测验证表明,经上述小波去噪后的沉陷模型精度得到显著改善,并有效保留了沉陷盆地的细节特征,沉陷模型的总体标准差在50 mm以内,能够满足西部矿区地表大变形监测的基本要求。进一步根据沉陷模型边缘的随机误差特征,提出了基于下沉坡度临界值的沉陷边界提取方法,为机载LiDAR技术用于西部矿区采煤沉陷的高效监测与精细建模提供了可行方案。

     

    Abstract: In the subsidence monitoring of coal mining areas,the conventional geodesy,InSAR and other remote sens- ing methods have some limitations. LiDAR technology can be used to scan ground subsidence area,and the fine fea- tures of surface subsidence basin can be quickly acquired by the superposition of multi-stage point clouds. However, the subsidence model based on the existing mainstream point cloud filtering and interpolation algorithms often contains significant noise,which limits the practical application of this technology in mining areas. The surface of a mining working face in Yushen mining area in China was taken as the experimental area. In view of its topographic fluctuation and low vegetation coverage geographical environment,the UAV LiDAR was used to obtain four sets of ground point cloud data in two phases. The improved method of mining subsidence modeling based on laser point cloud was studied by combining with the measured data of conventional surface movement. Through the comparison and analysis of DEM errors corresponding to commonly used point cloud interpolation and filtering algorithms respectively,including author- ized digital elevation model,inverse distance weighting,kriging,natural neighborhood,spline interpolation and progres- sive triangulated irregular network densification,multi-scale curvature classification,maximum local slope,and progres- sive morphological filtering,the results of using authorized digital elevation model interpolation and progressive triangu- lated irregular network densification fil-tering were better,but the generated initial subsidence model was still not accu- rate,which mainly included the model error caused by point cloud plane position error,non-ground point noise,point cloud interpolation error and water coverage range change. Based on the analysis of the above error distribution charac- teristics and the im-provement approach,an optimization scheme of the subsidence model denoising based on the wave- let threshold was proposed. Aimed at the different wavelet parameters of the subsidence basin and the non-subsidence region,the whole region were decomposed by using prior condition that the subsidence value of the non-subsidence re- gion was zero,the subsidence region were decomposed by the low-level wavelet,and then the two results were pro- cessed by embedding. The results showed that the accuracy of the subsidence model was significantly improved after the wavelet denoising,and the detailed characteristics of the subsidence basin were effectively retained. The overall standard deviation of the subsidence model was within 50 mm,which can meet the basic requirements of the large sur- face deformation monitoring in the western mining area. According to the random error characteristics of the subsidence model edge,a subsidence boundary extraction method based on subsidence slope was proposed,which could provide a feasible solution for the airborne LiDAR technology for the efficient monitoring and fine modeling of mining subsidence in the western mining area.

     

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