Research On Residual Movement And Deformation Monitoring In Coal Mine Area Based On SBAS-InSAR Technology

Coal mining not only contributes to the national economic and social development,but also causes serious damage to the ecological environment.At present,the observation of goaf in coal mines mainly focuses on the monitoring of surface movement and deformation in the process of coal mining.For the long-lasting residual movement and deformation period,there are few measured data,which limits the study of residual movement and deformation law in the mining area.Therefore,the monitoring and analysis of the residual movement and deformation of the goaf surface is particularly important to improve the law of surface movement and deformation after coal mining.The traditional monitoring methods currently used have some disadvantages,such as high cost,long time-consuming,low spatial coverage of surface deformation,difficult long-term preservation of monitoring points,and great environmental impact;Compared with traditional monitoring methods,synthetic aperture radar interferometry(InSAR)has the advantages of high efficiency,low cost,large range,and can be used in all weather conditions.It has a good application value for monitoring the residual movement and deformation of mining areas.Small baseline subset(SBAS)InSAR technology is a commonly used InSAR processing method,which can monitor continuous small deformation in a large area for a long time.In this paper,sbas-insar technology is used to monitor and analyze the residual movement and deformation in Fenxi Mining Area,and the improved GM(1,1)model is used to predict the residual movement and deformation,and a relatively complete residual movement and deformation law is obtained,which lays a certain foundation for predicting and evaluating the residual movement and deformation in goaf.The main research work and corresponding results are as follows:(1)The accuracy of the monitoring results obtained by SBAS-InSAR technology is verified,which proves that SBAS-InSAR technology has a good application prospect for monitoring the residual movement and deformation in coal mine area.Based on the actual mining information of six coal mines in Fenxi Mining Area and the 51 scene sentinel-1a data obtained,the data are processed with SBAS-InSAR technology to obtain the time series cumulative settlement results of the study area.The monitoring results of SBAS-InSAR are verified from both qualitative and quantitative aspects.According to the mining time of the working face,it is verified that the monitoring results of SBAS-InSAR can well reflect the process of surface settlement.The settlement value in the decline period obtained by SBAS-InSAR technology is compared with the settlement value in the decline period in leveling.The accuracy of the monitoring results of SBAS-InSAR is verified.The average root mean square error and standard deviation of all points are 14.12 mm and 19.12 mm respectively,The results show that SBAS-InSAR monitoring can meet the accuracy requirements of residual deformation monitoring with small shape variables in the study area,and prove the reliability of monitoring residual movement and deformation in mining area with SBAS-InSAR technology.(2)According to the mining time of the working face in the mining area,the monitoring results of SBAS-InSAR technology are processed to obtain the time-series cumulative settlement results of each working face in the residual movement and deformation period.The settlement value and settlement rate in the residual movement and deformation period are studied,and the settlement value of the working face mining the same coal seam is selected for regression analysis to establish the model of the residual movement and deformation period.The study area has a large span and contains a large number of working faces.According to the mining time of each working face,it can be found that the stopping time covers more than 20 years,and a relatively complete residual deformation law can be obtained.Through the analysis of the results of the residual movement and deformation period of each working face,it is found that within two to three years after entering the residual movement and deformation period,the settlement value of the working face tends to have a quadratic correlation with the residual movement and deformation time,and the quadratic term coefficient is very small;For the working face that has entered the residual movement deformation period for more than three years,the subsidence value tends to be linear with the subsidence time.The longer the stopping time of the working face,the closer the subsidence is to linear deformation,and the smaller the slope of the function is,the more stable the subsidence is.Within ten years,there is still small settlement in the working face until the settlement reaches the maximum.The regression analysis is made between the settlement value and stopping time of each working face from2017 to 2021,and the model of settlement value and settlement time in the residual movement deformation period lasting for 20 years is established.The research shows that the settlement value in the residual movement deformation period tends to have an exponential correlation with the stopping time as a whole,and the correlation coefficient is 0.994.Through the analysis of the settlement rate in the residual movement deformation period,it is found that when the residual movement deformation period is just entered,the settlement rate gradually decreases,fluctuates in this process,and the surface sinks slowly until it reaches the maximum value of surface settlement.(3)In view of the limitation of data updating when using sbas-insar technology to monitor surface deformation,the traditional GM(1,1)model is improved to realize the integration of settlement monitoring and prediction.Combined with the traditional GM(1,1)model and the law of surface subsidence in the mining area,the GM(1,1)model is optimized.Based on the settlement results obtained by sbas-insar technology and the GM(1,1)model theory,the integration of settlement monitoring in the period of residual surface movement and deformation and subsequent settlement prediction is realized.By comparing with the traditional GM(1,1)model,it is found that the optimized model can not only improve the fitting accuracy of measured values,but also get high-precision prediction values.It is found that the cumulative settlement value obtained by sbas-insar is highly consistent with the predicted value of the improved model.Applying the optimized model to predict the settlement value during the residual movement and deformation period of the mining area can effectively reduce the error of the classical GM(1,1)model,and provide a reference for the settlement monitoring and prediction during the residual movement and deformation period of the mining area.