Research On Dam Deformation Monitoring Method Based On Time-series InSAR

As an important part of dam safety management,dam deformation monitoring is an important means to acquire the safety status of dams and the premise for the safe operation of dams.Taking Xiaolangdi Dam as the study area,this paper selects 106Sentinel-1A data from March 31,2017 to October 17,2020 to study the deformation monitoring method of Xiaolangdi Dam based on Time-series InSAR technology.The influences of filtering algorithm,unwrapping algorithm and external DEM data in InSAR data processing on dam deformation monitoring results are compared and analyzed.According to the obtained dam deformation information,the deformation characteristics of dam at different positions and the periodic law of dam deformation and reservoir water level change are analyzed.The main work of this paper is as follows:(1)Applicability of different SAR data filtering and unwrapping algorithm.In this paper,the applicability of Adaptive,Boxcar,Non Local and Goldstein SAR filtering algorithms and Region Growing,MCF and Delaunay MCF phase unpacking algorithms in InSAR data processing for dam deformation monitoring are compared and analyzed.The experimental results show that the PSNR index and EPI index of Goldstein filter are better than the other three filters,and the comprehensive effect of suppressing speckle noise,fidelity and filtering efficiency is the best.The Delaunay triangulation network based on Delaunay MCF unwrapping algorithm is less affected by the low coherence pixels in the low coherence region and can minimize the phase jump.(2)Analysis of InSAR data processing accuracy for dam deformation monitoring of different external DEM.Three kinds of external DEM data,30 m SRTM,30 m AW3D30 and 12.5m PALSAR DEM,were selected to conduct experiments respectively,and the influences of image registration,leveling effect removal and geocoding on dam deformation inversion accuracy during InSAR deformation monitoring were analyzed.The experimental results show that the monitoring accuracy of PALSAR DEM is the best.The RMSE of PALSAR DEM is 6.64 mm lower than SRTM 30 DEM,and the accuracy is 23.65% higher than AW3 D 30 DEM,and 16.34 mm lower than AW3D30 DEM.Accuracy improved by 43.25%.(3)Analysis of monitoring accuracy of dam deformation by Time-series InSAR technology.PS-InSAR and SBAS-InSAR technologies were selected to conduct deformation monitoring experiments of Xiaolangdi Dam body,and the results of the two technologies were used as the basis for cross-validation.Experimental results show that PS-InSAR technology can obtain more accurate monitoring results than SBASInSAR technology in areas with high coherence and large deformation magnitude.However,when there are a large number of distributed scattering targets with low coherence,deformation information is easy to be lost,and SBAS-InSAR technology has better monitoring ability of distributed scattering targets.The accuracy of monitoring the small deformation of ground objects is similar to that of PS-InSAR technology.Compared with the measured leveling data,over 78% of the SBAS-InSAR statistical results showed that the error of deformation monitoring results was less than20 mm,and the root mean square error was 21.44 mm.The linear goodness of fit of the two results was 0.86,which verified the effectiveness of the Time-series InSAR technology in deformation monitoring of Xiaolangdi Dam.(4)Analysis of the deformation law of Xiaolangdi Dam.The monitoring results show that the vertical direction of the Xiaolangdi Dam presents the deformation characteristics of large deformation in the middle and small deformation in the shoulders.The average annual deformation rate of the dam center is between-20 and-25mm/y,and the maximum vertical cumulative settlement is 118 mm.The deformation along the flow direction is closely related to the change of the water level of the reservoir,and the deformation of each region shows obvious spatial heterogeneity.