Abstract: The deformation of expansive soil slope of the South-to-North Water Transfer Project is significantly affected by the dry-wet cycles such as rainfall and evaporation. The characteristics of expansion-shrinkage deformation and vertical displacement deformation of the expansive soil at canal top under dry-wet cycling are revealed, which provides a basis for the stability evaluation and treatment plan of the slope. Based on the experimental results of the expansion-shrinkage characteristics of expansive soil, combining the field observation data such as vertical displacement, water content, rainfall, evaporation and temperature monitoring, the correlation between the displacement of the canal top and the influence factor is analyzed, and a model for vertical deformation of the expansive soil at canal top under the action of dry-wet cycling is established. The results show that the expansion-shrinkage factor composed of water content, rainfall and evaporation are negatively correlated with the vertical displacement of the canal top. The vertical displacement component is smaller due to the expansion-shrinkage factor. The temperature factor is positively correlated with the vertical displacement of the canal top, and has a great influence on the vertical deformation of the canal top, which is the main factor affecting the deformation of the canal top. The slope excavation(time-effect factor) has a certain influence on the vertical deformation of the canal top at the initial stage of construction, but little influence on the vertical deformation of canal top after excavation.

Key words: South-to-North Water Diversion Project, expansive soil canal slope, expansion and contraction characteristics, correlation analysis, deformation model