Analysis Of Valley Width Deformation Characteristics Of Baihetan Hydropower Station Based On InSAR Technology

With the rapid development of China’s economic construction,the construction of high arch dam hydropower stations and the use of water resources for electricity production is a top priority in China’s construction sector.Valley width deformation is a very common phenomenon in high arch dam hydropower plants during water storage,which can lead to irregular deformation of the dam base and thus cracking of the dam,and is a key research object in the safety monitoring of high arch dam hydropower projects.The study area is located at the junction of Ningnan County,Sichuan Province and Qiaojia County,Yunnan Province.By studying the deformation characteristics of the reservoir bank valley width in the dam site area,we can understand the actual condition of the deformation of the reservoir bank valley width in the dam site area and effectively avoid a series of engineering disasters such as dam cracking caused by the deformation of the reservoir bank hills such as valley width deformation,as well as provide scientific prevention and control basis and information for the construction of arch dams in China.The paper applies SBAS-InSAR and Offset-Tracking remote sensing techniques to monitor the deformation of the reservoir bank in the dam site area,and discusses the deformation of the reservoir bank under the three different monitoring methods by constructing SSA,ADS,ADA function models and valley width models respectively based on the surface deformation analysed by SBAS-InSAR and Offset-Tracking techniques.By constructing SSA,ADS and ADA function models and discussing the deformation characteristics of valley width deformation under three different monitoring methods,the following results and conclusions were obtained:1 Using a total of 39 views of Sentinel-1 lift-track SAR image data,the one-dimensional line-of-sight deformation in the dam site area of Baihetan Hydropower Station from December 2020 to December 2021 was obtained using the SBAS-InSAR technique,with the lift-track monitoring data varying considerably due to factors such as flight track,imaging mechanism and terrain topography.Eight pairs of monitoring points were selected at the left and right banks upstream of the dam site to analyse the 1D deformation characteristics of the left and right banks during the storage period.The results showed that the deformation trends of the left and right banks in the dam site area during the storage period are generally different and the deformation rate is proportional to the reservoir level.2 Using Offset-Tracking technology,the one-dimensional azimuthal deformation of the dam site area was obtained from December 2020 to December 2021.According to the eight pairs of monitoring points on the left and right banks upstream of the dam site,it was found that the deformation trend at the left bank during the storage period was basically the same,and the deformation trend at the right bank was also basically the same,i.e.the impact of water storage on the same side of the reservoir bank was similar;the impact of water storage on the same side of the reservoir bank was different in magnitude.3 The SSA-based function model and the corresponding valley width model were constructed to analyse the valley width deformation displacement and the accumulated displacement of the left and right bank monitoring points during the storage period of Baihetan Hydropower Station,and to summarise the characteristic law of valley width deformation based on the SSA solution.4 Construct the ADS-based function model and the corresponding valley width model,analyse the valley width deformation displacement and accumulated displacement at the left and right bank monitoring points during the storage period of Baihetan Hydropower Station,and summarize the characteristic law of valley width deformation based on the ADS solution.5 The ADA-based function model and the corresponding valley width model were constructed,and a weighted stochastic model with Helmert variance estimation was added to the function model to improve the calculation accuracy of the three-dimensional surface deformation model and construct a three-dimensional surface deformation field.The valley width deformation displacements and the accumulated displacements of the left and right bank monitoring points during the storage period of Baihetan Hydropower Station are analysed,and the valley width deformation characteristic law based on ADA solution is summarised.6 A comparison with the valley width deformation measured by the valley width measurement line method shows that the analysis of valley width deformation characteristics based on InSAR technology can well reflect the trend of valley width deformation deformation,and the results of valley deformation measured by ADS method and valley width deformation measured by valley measurement line are more consistent.