The 3rd Badong International Geohazards Symposium (BIGS2021)

46 / 2021-11-14 21:53:44

Study on Deformation Characteristics of Landslide in Super Large Multi-level Reservoir—Taking Outang Landslide as an Example

Extra large multi-stage landslide；Three Gorges Reservoir；Outang Landslide；Step deformation；Groundwater

The spatial structure of super-large multi-level landslides is complicated, and the instability is serious, which is a difficult point in the study of landslide prevention. This paper takes the Outang landslide in the Fengjie section of the Three Gorges reservoir area as an example. Based on field surveys and GNSS professional monitoring data, analyze the response characteristics and deformation mechanism of landslides to influencing factors in combination with rainfall, reservoir water level and groundwater level. The result shows:(1)Heavy rainfall is the main inducing factor for the step deformation of Outang landslide. The annual deformation is concentrated from May to September. From the perspective of deformation and lag time, the trailing edge area of all levels of landslides is more sensitive to rainfall;(2)The deformation of the front edge of the first-class sliding body is controlled by the reservoir water level and rainfall. The stability of the first stage sliding body is reduced by dynamic water pressure during the falling period of the water level, and the stability of the first part of the water level rise period (145m→161m) is increased by the reverse osmotic pressure and negative displacement occurs.In the latter part of the ascent period (161m→175m), the anti-skid force decreases due to floating weight reduction, and the stability decreases;(3)The change of groundwater level in the landslide area caused by rainfall and the rise and fall of the reservoir water level is the direct cause of the step deformation of the landslide,reducing the rise of the groundwater level in the landslide area is the key to preventing such landslides.