Research On Extraction Method Of Surface Movement Parameters In InSAR Mining Area Based On Prior Conditions

InSAR technology can obtain time-series,planar surface deformation variables.It effectively makes up for the shortcomings of traditional monitoring methods to obtain surface deformation.The line-of-sight displacement obtained by the single-track differential interferometry method cannot calculate the real three-dimensional(3-D)deformation of the earth's surface.The mining subsidence deformation has a priori characteristics,which can be used to extract the deformation of the edge on the subsidence basin,the 3-D decomposition of the line-of-sight displacement,and obtain more accurate surface movement parameters of the mining area.This paper makes the surface of the Jinjitan coal mine face in Yulin,Shaanxi as the experimental area to study the method of extracting ground movement parameters based on InSAR deformation.The main content and results of this paper are as follows:(1)Use the priori characteristics of mining subsidence to effectively remove the influence of InSAR deformation errors.According to the a pr iori condition that the surface deformation of the non-mining-affected area of the mining area is zero,the wavelet transform is used to decompose and remove the low-frequency characteristic and high-frequency characteristic error of the differential interference phase of the ground point outside the subsidence area.In order to obtain the effective deformation of the boundary of the subsidence basin.Take two SAR images in the experimental area as an example to compare the unwrapping phase before and after removing some residual phases.It is found that the ground point shape variable in the non-mining affected area after correction is closer to zero.This shows that the method can effectively remove systematic residuals and noise effects in InSAR observations.(2)Based on the symmetry characteristics of the mining subsidence basin,the InSAR one-dimensional line-of-sight deformation is decomposed in 3-D.The main section along the strike and dip of the horizontal coal seam surface subsidence basin at the longwall working face can be divided into four symmetrical areas.The least squares equations of line-of-sight displacement and 3-D displacement are constructed based on four symmetrical points.The calculation of the 3-D displacement of the ground surface subsidence,direction and inclination is realized through program design.It was verified by simulated data and measured SAR data.The results show that the above decomposition method is suitable for the extraction of 3-D surface deformation variables under near-level coal seam mining.(3)On the basis of obtaining the 3-D deformation variables of the basin boundary,the dynamic and static movement parameters of the ground subsidence in the experimental area were extracted.Compared with the measured data of conventional surface leveling stations,the parameters such as the starting distance,duration,boundary angle and moving angle of the surface movement in the subsidence area extracted by the method in this paper are basically consistent with the measured results.This method proposed in this paper can not only extract horizontal displacement information,but also improve the accuracy of surface movement parameters extraction.It provides a feasible technical means for using monorail SAR data to obtain the law of surface subsidence in mining areas.