Monitoring Surface Deformation Of Closed Mine With An Improved Time-series InSAR Technology

In recent years,cutting overcapacity in China's coal sectors has been accelerating,and a large number of backward,inefficient and environmentally damaging coal mines have closed down to exit the market.At the same time,the safety and environment of the ground and underground of closed mines have got widely attention.The surface deformation of closed mines often lacks actual monitoring.The development of time-series InSAR technology can overcome the shortcomings of traditional measurement which is time consuming and inefficient,and at the same time it changes the influence of traditional DInSAR technology on the decoherence of spatial and temporal baseline,atmospheric delay,etc.Achieve full-time,all-weather and long-term monitoring of the mine surface,and the monitoring accuracy can reach centimetres or even millimeters.It will have a broad vision of application.The surface deformation of closed mine is small,and it is often in the same order of magnitude as the SAR noise.Therefore,studying the SAR noise processing method becomes the key to obtaining the accurate surface deformation of the closed mine.The purpose of this paper is to improve the filtering of interferogram and apply the time-series InSAR technology to monitor the surface subsidence of the closed mine.The main research work and achievements are as follows:(1)In order to improve the filtering effect of interferogram,according to Goldstein filter in frequency domain,an improved filter parameter model based on pseudo-noise ratio is proposed.Using stronger filtering for areas with lower image coherence to improve filtering efficiency.In order to further enhance the effect,repeated iterative filtering is also used.Combining simulated and real SAR data and interferogram filtering evaluation indicators,the effectiveness and superiority of improved filtering are confirmed.(2)Applying the improved filtering method to the StaMPS_SBAS technology,15 images of Sentinel-1A satellite were used to monitor the surface subsidence above the mining face.Compared the StaMPS_SBAS technology of the improved filtering method with the existing StaMPS_SBAS technology,it is proved that the improved filtering improves the quality of the interferogram and helps the correct phase unwrapping.The comparison between the monitoring results of the improved method and the observed data from the observation station shows that the improved method is reliable in obtaining the surface deformation of the mining area.(3)The StaMPS_SBAS technology with improved filtering method was applied to monitor the surface deformation of closed mines in Xuzhou area.At the same time,the monitoring results were compared and assisted by using TCPInSAR technology,and the surface subsidence data of the closed mine of Xuzhou North was obtained.The results show that the surface of the deep working face of the Jiahe Mine was subject to subsidence deformation before September 2017 and was uplifted in September 2017.Combined with the closure of the mine's geology and mining data and the distribution of the working face of the goaf,the sub-region studied the surface deformation,analyzed the possible causes of deformation,and assessed the influence of surface subsidence on the North Industrial Park of Xuzhou.(4)According to the surface subsidence monitoring data,the logarithmic function of the subsidence(or rise)of the ground surface and the stoppage of the working face after the closure of the mine is obtained,and the maximum subsidence is linear to the average depth of mining.It provides a technical basis for the assessment and prevention and control of subsidence disasters in the north of Xuzhou City.