Land Subsidence Monitoring And Risk Assessment Based On Time Series InSAR Technology In Nanchang City

With the development of economy and urbanization,a large number of high-rise buildings,highways,bridges,subways and other facilities have been constructed.However,while playing an important role in economic and social development,it causes ground subsidence of different degrees,and the impact of its hazards is widespread and the degree of impact is difficult to expected.Therefore,it is of great significance for urban ground deformation monitoring.Interferometric Synthetic Aperture Radar(InSAR)technology has such features as all-time and all-weather,which can obtain high-precision urban ground deformation information.In this paper,based on Sentinel-1A data from 2016-01 ?2018-12,PS-InSAR and SBAS-InSAR methods to obtain ground deformation information in the main urban area of Nanchang City and analyze the causes of inhomogeneous deformation.to establish a ground settlement risk evaluation system.The main research results are as follows:(1)This paper introduces auxiliary images that have high coherence with the images to be registered.Through the image transfer registration method,the azimuthal coherence when resampling the images to be registered is improved,thereby improving the long-term interval and low-coherence SAR images registration accuracy.(2)Collected C-band Sentinel-1A dual-polarization(VV and VH)images in Nanchang City,studied the differences in surface information obtained by different polarization methods at the same wavelength,and compared the interferogram,coherence,and phase unwrapping,deformation rate,etc.,the optimal polarization image is selected to improve the accuracy of surface deformation acquisition.It is found that VV polarization image is better.(3)The Pearson correlation between the two monitoring results of SBAS-InSAR and PS-InSAR is higher.The monitoring results proved to be reliable.The deformation trend in the main urban area of Nanchang City is northwest uplift and southeast subsidence.The deformation area includes Meiling National Forest Park uplift Zone(A),Nanchang West Railway Station-Nanchang International Sports Center subsidence zone(B),Dongxinxiang-Bayi Bridge section subsidence zone(C),Dengjiabu subsidence zone(D),and Nangang steel subsidence zone(E).Locating at the fault zone,ground deformation in A and D zones are related to fault zone geology.Subway,crowded urban buildings,etc.induce ground subsidence in Area B.The hydro-geological characteristics on the east bank of the Ganjiang River where Area C is located is more prone to land subsidence.Groundwater over-exploitation leads to land subsidence in Area E.(4)The land subsidence risk in the main urban area of Nanchang is evaluated from two aspects: the danger and vulnerability of ground subsidence.The spatial distribution of ground subsidence risk in main urban area of Nanchang City is as follows.There is not risk high area.With the line of Xinjian government-Dongxinxiang-Xianghu,the north belongs land subsidence higher risk area and medium area,and the southern mostly low-risk and low-risk area.