Abstract: To reveal the surface deformation law of a certain expansive soil canal section in the middle route of the Southto-North Water Diversion Project,based on the PS-InSAR technology,22 scenes of ascending and descending TerraSAR-X images covering the study area from June 2020 to February 2021 were used,and the multi-track time-series InSAR method was adopted to study the surface deformation law of a certain expansive soil canal section in the middle route of the South-to-North Water Diversion Project. This method not only can conduct all-round monitoring of the study area in a planar area,but also can reveal the temporal characteristics of deformation in the monitoring area,effectively making up for the deficiency of traditional leveling or GNSS monitoring methods that can only achieve single-point monitoring. The two-dimensional surface deformation evolution characteristics of the canal section in the study area from June 2020 to February 2021 were obtained,and the temporal and spatial distribution characteristics of surface deformation were analyzed and extracted. The results show that the average annual subsidence deformation rate of the canal section in the study area during the monitoring period is -25 to 20 mm/ a;among them,the deep-cut canal section shows a lifting trend,with an average annual deformation rate of 20 mm/ a,and the high-fill canal section shows a subsidence trend,with an average annual deformation rate of -25 mm/ a. Combined with the engineering geological conditions of the study area,it can be known that the main reason for the lifting of the deep-cut canal section in the study area is the expansion of expansive soil when it meets water;the main reason for the subsidence of the high-fill canal section is that the slope in this canal section is relatively steep. Under the combined action of the expansion of expansive soil when it meets water and the slope sliding,the sliding of the canal slope downward plays a major role,thus presenting different deformation trends. 

Key words: south-north water transfer project,PS-InSAR,TerraSAR-X,two-dimensional deformation,expansive soil