| Yunnan Province is located in the plateau mountainous area,with its special geographical location and complex topography,it is one of the most frequent areas of geological disasters in China.Various geological disasters,such as landslides,debris flows,collapses and ground subsidence are prominent,and the losses caused by geological disasters over the years are difficult to estimate.With the continuous development of science and technology,geological disaster investigation and research gradually changed from passive to active.How to discover and identify hidden dangers of geological disasters in advance and carry out effective monitoring and analysis to play a role in early warning and forecasting,reducing or even avoiding losses caused by geological disasters is a key issue that needs to be solved urgently in the field of ground disaster prevention.Because traditional measurement methods are labor-intensive,material-intensive,and optical remote sensing is difficult to quantitatively identify potential landslides.In SAR technology has the ability to monitor millimeter-level deformation on the surface in a wide range,and has been widely used in the field of geological disasters in recent years.The occurrence of landslide disasters is often the result of the coupling of multiple factors.There are external disturbance factors such as earthquakes,rainfall,and mining,and there are inherent disaster factors caused by regional geological conditions such as topography and geomorphology.Considering that in most areas of Yunnan Province,steep slopes,dense vegetation,extremely complex terrain,and developed mining industries,there are human-induced disturbance factors such as mining in most areas.The above factors have restricted the application of In SAR technology in the early identification and monitoring of landslides in Yunnan Province to a certain extent.Therefore,how to use the In SAR landslide monitoring technology reasonably and efficiently in this area is the issue of concern in this paper.In summary,this paper focuses on the application of In SAR technology in the identification,monitoring,and deformation analysis of landslides in mountainous areas of Yunnan.Select different representative regions for landslide identification and monitoring tests.The specific research contents and results are as follows:(1)In SAR principle and time series In SAR technology are introduced,and error sources and matters needing attention in landslide monitoring are analyzed.(2)Explains the principle of geometric distortion caused by side-view imaging of SAR system and its manifestation.The extraction method of geometric distortion area is given,which is helpful for researchers to select SAR images for different study areas.The influence of geometric distortion on the identification of In SAR landslides is analyzed,and an effective deformation information extraction method that takes into account the effects of geometric distortion is proposed,which is helpful to analyze the results of In SAR monitoring and improve the efficiency of landslide identification.(3)This paper used In SAR to monitor the slopes of a mountain area in Kafang Town of Yunnan Province that is affected by goafs.This paper proposed a new method that integrated the ground monitoring data of SBAS-In SAR,slope,and aspect.The deformation rate of LOS was obtained by SBAS-In SAR,and then it was converted into the vertical deformation rate.The result showed that the surrounding areas of Kafang town were notably affected by goafs,and that the vertical deformation rate of most areas was more than 10 mm/a.With the proposed method,we found that 16 of the 21 historical landslide points in the study area were identified as potential landslides while 5 were not identified(but also located in the deformation region).We conclude that our proposed method for identifying potential landslides was highly accurate and feasible.This study provides a way to detect potential landslides near the goafs,by determining whether mountain slopes are in a potential and inconspicuous sliding state or not,and accordingly,helps provide early warnings of landslide disasters.(4)In high mountain canyon regions,SAR geometric distortion in imaging side may has an inevitable impact on In SAR deformation information,so the effective deformation information acquisition is critical for landslide identification and deformation mechanisms analysis.The landslide deformation around the reservoir of Gushui Hydropower Station located in upstream of the Lancang River has been focused on in the study.Using SAR satellite parameters and topographic information,the visibility analysis of deformation in radar line-of-sight(LOS)direction has been carried out,and a method to obtain LOS effective deformation information based on the visibility analysis has been proposed.The small baseline subsets(SBAS)technique is used to process the L-band and C-band SAR data,and the area affected by the geometric distortion in the In SAR result is masked to obtain the deformation information of the effective deformation zone.The landslide identification analysis in the reservoir area has been carried out based on the effective deformation information in LOS direction.Thirteen landslides have been identified,and ten of them are new ones.A new large unstable area(New Zhenggang landslide)has been found near the Zhenggang landslide.The geological survey and displacement time series of the Zhenggang landslide reveals that it is in pull-type landslide mode.The impact of peak rainfall and cumulative rainfall during the rainy season on landslide deformation has been verified in this paper.It indicates that the cumulative precipitation is the dominant factor causing the deformation of the landslide.Generally,the landslide begins deformation acceleration period about 12 days after the peak precipitation.The results have shown that the proposed visibility analysis method for extracting the effective deformation information of In SAR results can significantly improve landslide identification and analysis in complex terrain. |
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