Deformation Monitoring And Safety Risk Assessment Of Urban Building Based On Radar Remote Sensing

As urbanization accelerates,human activities such as groundwater overdraft and underground space development accelerate the process of ground deformation,and at the same time,with the growth of building age,old houses or buildings become more numerous,leading to increased building risks.Therefore,urban building deformation monitoring,and thus building safety risk assessment,has become an urgent problem in urban construction.Traditional urban deformation and building safety monitoring mainly rely on level measurement and Global Navigation Satellite System(GNSS)methods,which are more accurate but require more labor and limited density of monitoring points.Compared with the traditional monitoring methods,Interferometric Synthetic Aperture Radar(InSAR)has the advantages of large range,high density of monitoring points and all-weather.At present,InSAR and time-series InSAR technology have been widely promoted and applied in the fields of urban deformation monitoring and so on.However,in building safety risk assessment,there are relatively few studies that link InSAR monitoring results with building safety risks.Inview of this,this thesis firstly carries out urban building deformation monitoring based on Persistent Scatterers InSAR(PS-InSAR)and Sentinel I 38-view SAR images in Nanjing city as an example.The reliability of PS-InSAR monitoring results is also verified by using level data and Small Baseline Subset(SBAS)technique.Based on the deformation monitoring,this thesis realizes the correlation between PS point deformation monitoring and building risk by extracting,classifying and screening the PS points on the building surface.Then,based on the evaluation criteria related to building safety risk identification,this thesis establishes a building safety risk assessment method based on eight safety risk indicators and evaluates the building safety risk in the study area and key areas of Nanjing.The main work and related results are as follows:1)Building deformation monitoring based on PS-InSAR technology using 38-view Sentinel-1A image data in Nanjing,and verification of the reliability of monitoring results using SBAS-InSAR technology and level measurement technology,respectively.The results show that the monitoring results of PS-InSAR and SBAS-InSAR techniques have good consistency and correlation,and the linear correlation coefficient of settlement rate of the same name point reaches 0.91;the RMSE of the difference between PS-InSAR and level measurement is 5.16 mm/a,which proves the reliability of PS-InSAR monitoring results in the study area.(2)Based on the PS-InSAR monitoring results,the extraction and classification methods of PS points on the building surface were established,and the correlation thresholds were determined based on the actual data.The safety risk indexes and evaluation criteria of buildings are determined by combining the relevant domestic norms and the actual conditions of Nanjing,and a set of building safety risk assessment methods are improved on the basis of the existing research.(3)Based on the safety risk assessment method of buildings in this thesis,the safety risk assessment was conducted in the study area and key areas of Nanjing,and the results showed that the largest percentage(31.26%)of buildings with risk level A(safe)in the study area of Nanjing.Among the buildings with PS deformation monitoring points,the percentage of grade A is 80.37%,which indicates that the buildings in the study area are safer overall.