| China’s water resources are unevenly distributed due to the distribution of groundwater and rainfall,showing a situation of rich in the south and poor in the north.In order to balance the uneven distribution of water resources,the South-to-North Water Transfer Central Project was officially opened in December 2014.The water was transferred from Danjiangkou Reservoir to 14 cities along the route,including Zhengzhou,Shijiazhuang,Beijing and Tianjin.The project has alleviated the water shortage and optimized water allocation in China’s North China Plain.About 1/3 region of the South-North Water Transfer Line crosses the swelling soil(rock)area.The volume and strength of the swelling soil will change when it experiences precipitation and evaporation,increasing the possibility of slope instability along the line.In this context,it is necessary to identify and monitor the unstable swelling soil slope with purpose of mitigating the influence of landslide.The main contents of the paper are as follows:(1)Time-series deformation along the South-North Water Diversion Central Project was obtained.Based on the 869 Sentinel-1A SAR image from March 2017 to December 2020,timeseries InSAR technique was used to obtain the time-series deformation along South-North Water Transfer Central Project.The results show that most of the areas are in stability,with the maximum deformation rate up to 155 mm/y,among which Xinxiang,Anyang,Handan,Xingtai and Beijing present larger deformation values;(2)29 unstable expansive soil slopes in the South-North Water Transfer Central Project were identified.The 29 unstable expansive soil slopes on both sides of the channel were identified by integrating the time series deformation,swelling soil distribution,slope and slope direction.The sections at the head of the channel,Handan and Change were selected for specific detailed analysis;(3)Time series deformation analysis of swelling soil slopes was carried out.Taking the Nanyang-Pingdingshan section swelling soil slope as an example,the time series from 2007 to2010 and from 2015 to 2020 before and after water supplying were obtained by using ALOS as well as Sentinel 1A images.The results showed that significant changes were produced on both sides of the channel before and after water access.On this basis,the time series deformation was found to be consistent with the deformation pattern of expansive soils,showing a repeated deformation trend of subsidence and uplift.Considering most scholars only qualitatively analyze the influence of meteorological factors on the deformation of expansive soil,the influence of rainfall and temperature on the deformation of expansive soil in the selected area is calculate quantitatively by using wavelet transform through the purchased meteorological data.The results show that the deformation of expansive soil in a certain period of time is not completely dominated by meteorological factors,and there are other influencing factors;the changes of meteorological factors always precede the deformation of expansive soil,and there is a certain lag in the deformation of expansive soils. |
