Study On Surface Subsidence Monitoring In Mining Area Based On InSAR Technology

China is one of the countries with the richest coal resources in the world.The exploitation of coal resources promotes the rapid development of China's economy.However,the surface subsidence caused by a large number of underground mining has a serious impact and harm on the mining environment.Therefore,it is of great theoretical and practical value to carry out the research on surface subsidence monitoring in mining areas for "coal mining under buildings,railways and water-bodies" and to formulate scientific and reasonable environmental protection measures.Although the traditional mining area surface subsidence monitoring method has high measurement accuracy,it needs a lot of manpower and material resources for large-scale deformation monitoring by laying observation lines,and it is difficult for long-term maintenance of measuring points.Interferometric synthetic aperture radar(InSAR)technology has become one of the common methods for monitoring land subsidence because of its all-day,all-weather,high accuracy,and wide range.The results of InSAR interferometry have a high spatial and temporal resolution,which can reach centimeter or even millimeter level accuracy and can meet the accuracy requirements of surface subsidence monitoring in the mining area.In this paper,the related problems of InSAR technology in mining area surface subsidence monitoring are studied.The main research contents and achievements are as follows:(1)Discusses the influence of DEM(Digital Elevation Model)on the surface subsidence monitoring of DInSAR(Differential InSAR).Taking the Binchang mining area as the research object,four kinds of DEM are selected as reference elevation data,and two groups of sentinel-1A data are processed based on DInSAR technology.The comparison and analysis of different DEM data,DInSAR monitoring results,GPS(Global Positioning System)measured data,and monitoring results show that the accuracy of DInSAR monitoring results is the highest when NASA DEM is used as reference elevation data.(2)Discusses the applicability of different time series InSAR in mining area surface subsidence monitoring.Taking Mengcun coal mine in Binchang mining area as the research object,three kinds of time series InSAR technologies including PS DInSAR(Persistent Scatterers DInSAR),SBAS DInSAR(Small Baseline Subset DInSAR),and SBAS DInSAR selected by optimized GCP points were used to process the 30 Sentinel-1 A data in the study area from January 11,2018,to December 25,2018.Through the analysis of the monitoring results of different time series InSAR technology,five GPS measured data from June 9,2018,to November 29,2018,are selected to verify the monitoring results of different time series InSAR methods.The results show that the SBAS DInSAR technology,which optimizes the selection of GCP points,has the highest accuracy.(3)In-depth discussion of the SBAS DInSAR mining area surface subsidence monitoring method based on optimized GCP point selection.SBAS DInSAR based on optimized GCP point selection processed 98 Sentinel-1A data of Binchang mining area from October 23,2014,to May 6,2019,and obtained the annual average settlement rate map and time series cumulative settlement of the study area amount.The selected time span is from June 29,2018,to March 9,2019,and a total of 6 GPS measured data are compared with the monitoring results of the corresponding time period.The results show that the maximum annual average settlement rate and maximum cumulative settlement of the mining area are-97 mm/a and-387 mm,respectively;the average root means square error(RMSE)and average correlation coefficient(r)between GPS and monitoring results are 2.3 cm and 0.944,respectively.The feasibility of the application of the SBAS DInSAR technology,which optimizes the selection of GCP points,in the study area,and the accuracy of the monitoring results are verified.