| Ground subsidence not only threatens urban security,but also causes great losses to local ecological environment and social economy.Changzhou is located in the ground subsidence zone of the Yangtze river delta,which is also one of the most economically developed areas in China.It is of great significance to carry out ground subsidence monitoring in Changzhou city to map and detect ground subsidence,so as to provide help to decision making for disaster prevention and reduction.The time-series InSAR technology developed in the past 20 years has been widely used in surface deformation monitoring due to its characteristics of all-day,all-weather,high precision,high spatial coverage and high spatial and temporal sampling rate.Based on the time-series InSAR technology,this paper used 23 TerraSAR-X(2012-2013)descending image data and 36 Sentinel-1A(2015-2018)ascending image data to derive the surface deformation of Changzhou.The distribution maps of ground subsidence rate and the cumulative surface deformation map of Changzhou area in 2012-2013 and 2015-2018 were obtained,and the temporal and spatial variation characteristics of subsidence in this area were analyzed.The main research work and achievements are as follows:(1)The SB AS InSAR method was used to derive the time series surface deformation of 23 high-resolution TerraSAR satellite X-band SAR data from 2012 to 2013,and the annual average subsidence rate and time series surface deformation map of Changzhou during this time period were obtained.The results show that during the observation period,most of the Changzhou City was stable,while serious ground subsidence were detected in the southeast of Wujin District which were connected into a slice.(2)The SBAS InSAR method was used to derive the time series surface deformation of 36 scenes Sentinel-1A data from 2015 to 2018,and the annual average subsidence rate and time series surface deformation map of Changzhou in this period were obtained.The results show that during the observation period,compared with the surface deformation characteristics of 2012-2013,the overall deformation characteristics of the whole area approximately remained the same with that of 2012-2013,while a slight rebound were detected in some district.The subsidence in the southeastern part of Wujin District had slowed down and the uplift phenomenon was also detected in some areas of Wujin District.(3)The PS-InSAR technology was used to monitor the surface deformation in Wujin District,and it was found that there were many important traffic lines running through the obvious surface deformation area.Some ground subsidence around the important traffic lines had exceeded the safety threshold.Therefore,it is necessary to enhance the monitoring of these heavily settled roads besides routine monitoring,providing a scientific basis for the stability evaluation of linear engineering during operation.(4)The spatial-tempo statistical analysis of the surface deformation of Changzhou City from 2012-2013 and 2015-2018 were conducted.The results revealed the temporal and spatial evolution of the surface deformation during the monitoring period in Changzhou.By comparing with the historical monitoring results of the region,it is found that the monitoring and analyzed results of this paper have good consistency and continuity with the historical subsidence monitoring results in this region.Based on the history of ground subsidence and hydrogeological background in the study area,the temporal and spatial evolution characteristics and laws of ground subsidence in Changzhou area about the past 50 years are summarized.The comprehensive analysis shows that the ground subsidence in the study area has been effectively controlled after the groundwater is completely banned,the subsidence rate was slowed down,and even rebound occured,showing a slight subsidence and even a rebound pattern. |
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