Monitoring Technology And Method Of Karst Surface And Structure Deformation Based On Radar Interferometry

Wuhan is a megacity in China with a population of more than 10 million.It has experienced significant development in the past decades.At the same time,six NWW-SEE trending concealed karst zones are distributed from Tianxingzhou in the north to Hannan District in the south,and the Quaternary loose sediments directly cover each karst zone.The Yangtze River and Hanjiang River pass through the city,and a large number of urban lakes are scattered among it,and companied with the intensive municipal engineering excavation and industrial construction water mining,which make Wuhan becomes one of the largest cities prone to karst collapse and surface subsidence in China.In addition,under the excitation of natural environment,the vibration of large-scale structures(such as high-rise buildings,bridges,etc.)changes in a variety of ways and instantaneously.Real-time or quasi real-time monitoring of the dynamic vibration characteristics of such structures and extraction of their operating modal parameters(natural frequency,damping ratio,modal shape)are very important for their safe operation,maintenance and management decision-making.Multi-temporal InSAR technology,as a brand-new space observation technology,has the characteristics of all-weather,all-weather,wide coverage,long spanning time,and high measurement accuracy,so it is particularly suitable for application in large-scale,slow and uniform deformation scenes,Such as urban ground subsidence,unstable slopes,karst surface collapse,etc.However,for small areas or single deformation bodies,such as creep landslides,rock collapses,dynamic vibration of large structures and health monitoring,irregular distribution locations,diversified deformation factors,and rapid deformation problems,ground-based radar interferometry(GBRI)as the realization of spaceborne SAR on the ground,it has the characteristics of simple and flexible installation,high sampling rate,real-time processing,etc.,so it is particularly suitable for urban local landslides,local karst surface collapse and deformation and health monitoring of single structures.In this paper,the karst surface collapse / subsidence in Wuhan City and the Liusha Peninsula landslide in Nanning City,Wuhan Baishazhou Bridge and Lvdi Center were taken as the research objects.We study the quantitative evaluation of Wuhan karst surface collapse(subsidence)factors based on StaMPS-MTI technology and the deformation monitoring of urban landslides and structures based on GBRI.The main research contents include:1)This paper systematically introduces the formula derivation and data processing flow to derive ground elevation and deformation displacement by spaceborne InSAR,D-InSAR and GBRI technology,and summarizes the error sources,models and corresponding removal or weakening measures in deformation monitoring.2)We first summarize and deduce the amplitude offset polynomial registration algorithm,PS / SFDP point selection strategy and tropospheric delay estimation model based on "phase-elevation" linear relationship in StaMPS-MTI technology,and on this basis,a "phase-elevation" tropospheric delay correction method based on multi-scale band pass filtering is proposed.Then,44 Sentinel-1A unwrapping interferograms in Iran are used to verify the tropospheric correction effect of this model and the products of the GACOS tropospheric delay.The results show that the RMS of the phase unwrapping based on the proposed-model is much smaller than that based on the GACOS method.Finally,the proposed-tropospheric model is integrated into the StaMPS-MTI processing flow.3)Based on the comprehensive analysis of the existing mosaic methods of multi-temporal InSAR results,In this paper,the influence of radar incidence angle deviation and the difference of reference points in the processing of adjacent orbit independent multi-temporal InSAR is considered.We propose an adjacent track StaMPS-MTI deformation rate mosaic method based on block sampling to find the weighted rate difference mode,and use this method to stitch the multi-temporal InSAR results of Wuhan TerraSAR-X Track 8 and Track 9.The weighted velocity difference mode of the adjacent orbit overlap region is 1.37 mm / yr,and there is no obvious rate gradient jump.4)Aiming at how to establish the coupling relationship of surface deformation displacement,hydrological factors(groundwater,water level of the Yangtze River,rainfall,etc.)and karst geological conditions,and then quantify the factors of karst surface subsidence(sinking)in Wuhan.The displacement water level coupling analysis based on the Cross Wavelet Transform and the building density index(IBI)method are introduced to analyze or quantify the collapse / subsidence of karst surface in Wuhan from the aspects of industrial production water exploitation,karst and hydrogeological conditions,pore / karst water change,municipal construction,building load,etc.The results show that the land subsidence in the north of Wuhan has a high spatial correlation with the spatial distribution of industrial production areas;In Baishazhou area,where karst is highly developed,under the combined effect of the typical "upper sticky and lower sand" overburden dual structure,the rapid hydraulic circulation of the Yangtze River water-pore water-karst water on the first terraces on both sides of the Yangtze River,the pumping of the above-ground engineering construction and the excavation in the underground 30 m space,the process of subsurface suffusion and vacuum suction in Baishazhou area are accelerated,which lead to many karst surface collapses in history and surface subsidence on this karst belt today;In general,the area with large subsidence rate corresponds to large IBI value,but it can't be shown that the building load is the dominant factor of land settlement,because even in the area with the most significant settlement rate,the maximum correlation coefficient between IBI and surface deformation rate is only 50%.5)For the GB-SAR deformation results of small scenes,they are usually displayed in the form of two-dimensional bitmap directly in radar coordinate system or superimposed on DEM,which is not conducive to the interpretation of deformation results.Especially when the deformation needs to be matched to specific geographical scenes,the virtual reality panoramic technology(VRP)is proposed to project the scene line of sight to deformation to the research area map collected based on UAV Like the generated panorama.By using this method,the GB-SAR deformation result of Liusha landslide in Nanning is superposed with the 3-D reconstruction model of topography and building in the landslide area,and the displacement time history 3-D expression of Liusha landslide is realized.6)Aiming at the problem that FFT based spectrum identification method is not sensitive to high-order frequency and has large extraction error when extracting multi frequency vibration parameters of structure,a sequential quadratic programming optimization genetic algorithm(SQP-GA)is proposed,which takes into account the global and local search ability.The algorithm is applied to the dynamic vibration monitoring of Baishazhou bridge and Wuhan Lvdi Center,SQP-GA method can not only extract the main frequency of higher-order structure vibration,but also obtain the sine and cosine vibration component under each main frequency response,so as to realize the inversion of vibration time history of structure under natural environment excitation.In addition,based on the displacement time history of Wuhan Lvdi center obtained by two GB-RAR in the orthogonal direction,and the deformation monitoring of Lvdi financial city buildings based on high-resolution TerraSAR-X image,the mode shape of Lvdi center and the fine monitoring of its affiliated buildings are obtained.