Revival Mechanism And Deformation Prediction Of Typical Accumulative Landslide In The Three Gorges Reservoir

1 to 3 years, after the high water level and normal water of the Three Gorges Reservoir, are active period of the reservoir bank rebuilding and the landslide deformation activity in reservoir area, and a large number of accumulative Landslides will revive. As known, the landslide has the features of large scale, large quantities and wide distribution and so on, so once the landslide slips into the Yangtze river, it will result in the heavy casualties and economic losses. Additionally, the serious consequence is caused by that landslide induced secondary disasters surge, so it has important theoretical and engineering significance to study the revival mechanism and deformation prediction of the accumulative landslide.In view of the above situation, the accumulative landslide deformation features on the responses of the reservoir water level variation was studied based on monitoring achievements. As the internal cause inducing the accumulative landslide deformation, engineering geological model was further researched, and as the external cause of revival deformation of the accumulative landslide, effect mechanism of groundwater was further discussed, and then deformation prediction model of accumulative landslide was established, it has reference for disaster prevention and mitigation.In this paper, the research contents and results are shown as follows.(1) Accumulative landslide deformation features on the responses of the reservoir water level variation. According to the changed process level of reservoir water in the Three Gorges Reservoir, reservoir water level on landslide location was determined, and characteristic curves (e.g. deformation, pour water pressure) of two accumulative landslide (e.g.YuHuangge landslide, Hefeng landslide) with water level fluctuations was get to study typical landslide feature rules on the responses of the reservoir water level variation. Significant deformation of YuHuangge landslide occurred at water level rising phase.However, significant deformation of Hefeng landslide occurred at water level drawdown phase.(2) Engineering geological model of accumulative landslide. Statistics of 89 accumulative landslides in Zigui-Wanzhou section in Three Gorges Reservoir shows the distribution rules of volume, terrain and physiognomy, formation litho logy, slope types. Four major controlling factors involving fabric characteristics of sliding mass, dynamic causes, deformation characteristics and developmental stages, and the based landslide engineering geological model was established. As the most accumulative landslide is in the influential area of water level changes, detailed dynamic causes consider the action mode of the reservoir water on different types of landslide, so dynamic causes were further divided into three categories such as float effect weight reduction, penetration, float weight and penetration (mixed), which refine the basic geological model of accumulative landslide. Use the above basic methods and theory building geological model and get the basic geological model of Yuhuangge landslide that it is the artificial reservoir float effect weight reduction soil sliding mass and rock bed landslide which belong to the freshmen gestation period and is progressive traction, in addition, the basic geological model of Hefeng landslide is the artificial reservoir osmotic pressure soil and rock bed (and soil bed) landslide that it is the revived gestation period and is dynamic traction.(3) Mechanical effect of groundwater water in the accumulative landslide revival process. Due to the different permeability of rock and soil mass of the landslide itself, reservoir fluctuations has different effect on landslide body. Based on the normal changed water level of a hydrological year of Three Gorges reservoir, the groundwater seepage line of different permeable landslide body with the rising and falling process of water level was analyzed, the groundwater effects were divided according to the distribution of invasive lines at different stages of water level and different types of landslide. Different mechanical effect of groundwater have different effect on the landslide stability from qualitative view, so reservoir-landslide was future divided into float effect weight reduction, penetration, float effect weight reduction and penetration (mixed).When the water level rises, if permeability coefficient k>10-4m/s, a≤5°, effects of groundwater acts as float weight, so it favorable to landslide stability, if permeability coefficient 10-5m/s