Monitoring And Analysis Of Surface Subsidence And Building Deformation By Radar Interferometry

Deformation monitoring and analysis is an important basis for the safety assessment and early warning of disasters(e.g.,surface subsidence,building collapse and landslides etc.).Aiming at potential disasters,conduct surface subsidence and building deformation monitoring in important areas,and perform safety analysis and early warning based on information such as deformation information and deformation impact factors of monitoring objects to avoid or mitigate disaster losses,which has important scientific significance and social benefit.Currently,conventional deformation monitoring and analysis methods(e.g.,leveling,GNSS,acceleration sensors,etc.)are limited by the factors such as low spatial resolution,difficult deployment of target monitoring points,and high operating costs,which makes it difficult to achieve large-scale and high spatial resolution deformation monitoring and analysis.In recent decades,radar interferometry technique as a new space geodesy technique,with its advantages of non-contact,all-weather,all-day and high spatial-temporal resolution,overcomes the shortcomings of the above-mentioned conventional methods.However,it also has some limitations.For example,for spaceborne radar interferometry technique,due to the influence of the long repeat cycle of satellite,atmospheric delays and other factors,it is difficult to satisfy the extraction of high temporal resolution and high-precision deformation information in local areas or buildings.Although ground-based radar interferometry technique can effectively overcome the shortcomings of spaceborne radar interferometry technique,ground-based radar system for high-frequency data acquisition,affected by environmental change,the instrument error and other factors,both white noise and colored noise will be present in the radar signal,the existence of the above two kinds of noises will affect the accurate estimation of deformation information.Radar interferometry technique can only achieve the geometric deformation information of the monitoring objects.In order to more reasonably and reliably evaluate the safety of the disaster,we need to combine the physical influence factors of the monitoring objects for scientific explanation and evaluation.Based on the above problems,in this paper,we elaborated the deformation inversion model and the basic error sources in the spaceborne and ground-based radar interferometry technique.We studied the deformation analysis methods combining the geometric deformation and the influence factor information and established surface subsidence analysis methods based on multi source data and multiple methods.The noise characteristics in radar signal were studied,and the estimation model of radar signal deformation information which can simultaneously take into account the effects of white noise and colored noise was established.We studied monitoring and analysis method for dynamic characteristics of super high-rise buildings based on GB-RAR.The main research content and contribution of this paper are as follows:(1)In this paper,the basic theory of radar interferometry technique was systematically elaborated,including the imaging principle and imaging characteristics of spaceborne and ground-based radar interferometry,InSAR height measurement technique,DInSAR deformation monitoring technique,time-series InSAR technique,radar interferometry basic error sources and their processing methods.(2)A surface subsidence analysis method based on the Multi-temporal Interferometric Synthetic Aperture Radar(MTInSAR)and Gravity Recovery and Climate Experiment(GRACE)was proposed in this paper.Taking Beijing area as the research object,the surface subsidence and the correlation between surface subsidence and groundwater changes in this area were studied.The MTInSAR technique was used to retrieve the surface subsidence velocity field and spatial distribution in Beijing area using 18 ENVISAT ASAR images from 1 August 2007 to 29 September 2010.The MTInSAR-derived subsidence results were verified by leveling at an accuracy better than 5 mm/year.Based on the verified MTInSAR subsidence results,a prominent uneven subsidence was identified in Beijing.Specifically,most of the subsidence velocities in the downtown area were within 10 mm/year,and the largest subsidence was detected in Tongzhou,with velocities exceeding 140 mm/year.Furthermore,GRACE data were used to derive the groundwater change series and trend.By comparison with the MTInSAR-derived subsidence results,comparison results show that the long-term decreasing trend between groundwater changes and surface subsidence showed a relatively high consistency,and a significant impact of groundwater changes on the surface subsidence was identified.Additionally,the spatial distribution of the subsidence funnel was partially consistent with that of groundwater depression,i.e.,the former possessed a wider range than the latter.(3)In this paper,wide-area surface subsidence characteristics in Wuhan was investigated using 15 Sentinel-1A Terrain Observation with Progressive Scans(TOPS)SAR images acquired from 11 April 2015 to 29 April 2016 with the Small Baseline Subset Interferometric SAR(SBAS InSAR)analysis method.The subsidence change maps of major subsidence areas in Wuhan were obtained,and the correlations between surface subsidence and urban construction,precipitation,industrial development,carbonate karstification and water level changes in Yangtze River in Wuhan were analyzed and established.The inversion surface subsidence results based on Sentinel-1 A were validated by 110 leveling points at an accuracy of 6 mm/year.Prominent uneven subsidence patterns were identified in Wuhan.Specifically,surface subsidence rates ranged from-82 mm/year to 18 mm/year,and maximum subsidence rate was detected in Houhu areas.Surface subsidence time series presented nonlinear subsidence with pronounced seasonal variations.Comparative analysis of surface subsidence and influencing factors indicated a relatively high spatial correlation between locations of subsidence bowl and those of engineering construction and industrial areas.Seasonal variations in subsidence were correlated with water level changes and precipitation.Surface subsidence in Wuhan was mainly attributed to anthropogenic activities,compressibility of soil layer,carbonate karstification,and groundwater overexploitation.The spatial-temporal characteristics of wide-area surface subsidence and the relationship between surface subsidence and influencing factors in Wuhan were given in the results of this study.(4)Aiming at the situation of the effects of both the white noise and colored noise are present in the extraction of deformation time series based on ground-based radar high-frequency data,a radar signal deformation information estimation model,which can simultaneously take into account the effects of white noise and colored noise,was proposed in this paper based on maximum likelihood estimation.The proposed model was applied to the safety monitoring and analysis of East Lake High-tech Bridge during Wuhan Metro Line 11 shield tunnel crossing underneath this bridge.The subsidence time series of the bridge was derived through ground-based interferometric radar,and the subsidence time series was verified by leveling at an accuracy better than 0.33 mm.Furthermore,white and colored noises were detected in the denoised subsidence time series through a power spectral analysis and Maximum Likelihood Estimation(MLE).For the subsidence time series of Nos.7 and 8 piers,the colored noise amplitudes were 0.3824 mm and 0.6261 mm,respectively,and the white noise values were 0.0414 mm and 0.0610 mm,respectively.Accurate subsidence rates and accumulative subsidence were derived through estimation model by using the noise characteristics in the subsidence time series.The subsidence rates of Nos.7 and 8 piers were-0.0122 ± 0.0060 mm/hour and-0.0065± 0.0058 mm/hour,respectively,and the accumulative subsidence values were-0.6365 mm and-0.3370 mm,respectively.The study reslts suggest that the bridge is stable and safe during monitoring.(5)This paper took the third highest building in the world(636 m)under construction(Wuhan Greenland Center)as the research object,a set of technical methods for monitoring and analyzing the dynamic characteristics of super high-rise buildings based on GB-RAR were researched and established.The GB-RAR technique was used to monitor the dynamic deformation information of the building from north-south and east-west direction.Based on the wavelet analysis and periodogram method,the accurate dynamic characteristics information of the building,such as horizontal displacement,oscillation amplitude,displacement trajectory and significant frequency,were extracted.During the study period,the maximum horizontal oscillation amplitudes of north-south and east-west direction at the top of the building were 18.84 mm and 15.94 mm,respectively,and the accuracy reached submillimeter level.Meanwhile,the natural frequency of the building was detected as 0.20 Hz.Because the building was affected by various factors(e.g.,construction vibration,wind load,temperature,etc.),the building was also significantly affected by other frequencies.