Characteristic comparison of seepage-driven and buoyancy-driven landslides in Three Gorges Reservoir area, China

The Three Gorges Hydropower Station is the largest hydropower station worldwide with the impoundment of the 660-km long reservoir. More than 500 landslides have been triggered by the reservoir water level fluctuation since the first impoundment in 2003. The classification of the reservoir affected landslide (seepage-driven and buoyancy-driven landslides) is crucial for landslide early warning and risk management. There are still no classification criteria for the reservoir landslide in TGRA. In this study, based on the long term in-situ monitoring, numerical simulation and field investigation methods, two typical reservoir landslide of Tangjiao landslide (seepage-driven) and Tanjiahe landslide (buoyancy-driven) in TGRA were taken as study cases. The comparative analysis of the response relationship between the long term deformation and the influencing factors were carried out. It can be found that the intensive deformation of Tangjiao landslide occurred during the rapid drawdown period of the reservoir water level, while Tanjiahe landslide has been deforming in the whole water year. Moreover, by analyzing the cumulative displacement curve, the permeability of the sliding mass, and the sliding surface of six reservoir landslides in TGRA, the classification criteria for seepage-driven and buoyancy-driven landslides in TGRA were proposed.