On the Soil Slope Failure Mechanism Considering the Mutual Effect of Bedrock and Drawdown

In reservoirs and embankment areas, frequent water-level fluctuations, especially water drawdowns, often produce instability problems or landslides in the slopes overlying bedrocks. A series of centrifuge model tests were conducted on three slopes overlying bedrocks with different shapes and a slope without the bedrock under drawdown conditions. Full-field displacement of the slopes was obtained for analyses using an image-based system during the tests. The slip surfaces of the slopes overlying bedrocks all emerge at the top of the slopes and then extend to the bottom under drawdown conditions. The slip surface of the slope without the bedrock is the bounding surface for those slopes overlying bedrocks under drawdown conditions. The drawdown-induced deformation area of the slopes is first restricted to a certain range and then gradually expands during drawdown and finally stabilizes. The coupling development of the deformation localization and local failure during drawdown illustrates the progressive failure mechanism of the slope overlying the bedrock. Different shapes of the bedrocks would change the deformation localization characteristics of the slopes and hence significantly change the failure characteristics of the slopes, such as the slip surface, failure process, and safety limit.