Abstract: The stability and the deformation of the expansive soil canal are closely related to each other. Several landslides occurred during more than 2 years of the expansive soil tests in a large water diversion engineering project. The inclinometer was used in the in-depth lateral deformation monitoring. Based on the analysis on the extrinsic and intrinsic connections between the stability and the deformation of an expansive soil canal, it is suggested that the deformation rate and the accumulative displacement are the main early warning indices, and the development time of the deformation, the change of environment and the response of the slope are the reference indices in distinguishing the expansive soil canal instability. Moreover, the forecast and the early warning method of the expansive soil landslide is proposed, which provides a reference for the rational evaluation of the safety state and the development trend of expansive soil canal slopes.

Key words: Expansive Soil, Test Section, Canal Slope Sliding, Deformation Monitoring, Early Warning Method