InSAR Three-dimensional Displacement Inversion Model Of Surface In Mining Area Based On Subsidence Symmetry

Real-time monitoring of surface deformation caused by coal mining is of great significance for building protection and ecological environment restoration in mining area.synthetic aperture radar interferometry(InSAR)technology has become an important means of surface deformation monitoring in mining area.The radar line-of-sight(LOS)displacement obtained in InSAR monitoring is a vector superposition of the vertical,north-south,east-west three-dimensional displacement of the surface point.The decomposition of LOS displacement into surface subsidence and horizontal displacement along the strike and tendency of working face is the basis for studying the law of mining subsidence and obtaining the parameters of surface movement.At present,the main methods of using InSAR LOS displacement to retrieve the three-dimensional displacement of mining subsidence are as follows: using three SAR images of different orbit satellites to establish LOS displacement equations to solve the three-dimensional displacement component;According to the prediction model of mining subsidence,the horizontal displacement of the surface is regarded as the correlation function of subsidence,and the subsidence and horizontal displacement are solved by a single SAR image,or the influence of horizontal displacement is directly ignored and the LOS displacement is projected as the subsidence component.On the basis of analyzing the limitations of the above methods,based on the mining subsidence theory and the measured data,this paper demonstrates the basic characteristics of the surface subsidence and horizontal displacement of the near-horizontal coal seam mining on the symmetry of the main section of the moving basin.According to the symmetry principle of surface movement,the geometric equations of multi-period InSAR LOS superimposed displacement at symmetric points are established,and the equations are superimposed and treated by difference,and the function model of three-dimensional displacement of mining subsidence inversed by LOS displacement is derived.In the process of advancing the working face,because of the hysteresis of thesurface movement,the center of the dynamic subsidence basin tends to the side of the open hole.according to the characteristics that the surface subsidence of the central moving basin reaches the maximum and the horizontal displacement approaches to zero,Based on the superposition and difference of LOS displacement of adjacent pixels,the dynamic center position of the surface moving basin is automatically searched,so as to realize the decomposition of the dynamic three-dimensional displacement of the surface in the process of advancing the working face.The algorithm implementation and verification of the above inversion model are carried out based on Matlab platform.Firstly,the displacement values of surface subsidence,strike and inclination above the working face are simulated and calculated,and the LOS displacement is synthesized according to its spatial geometric relationship.Then the LOS displacement is decomposed into the displacement in the above three directions by using the derived three-dimensional displacement inversion model.The verification shows that the derived three-dimensional displacement inversion model and program run correctly.At the same time,the surface multi-scene Sentinel data of a mining face are selected for differential interference processing by Gamma software,and the InSAR LOS directional displacement is decomposed according to the above model.The results show that the inversion results of this model are basically consistent with the measured data,which is obviously superior to the method of directly decomposing surface subsidence without horizontal displacement,and has good universality and application value.