Control Of The Sliding Surface Shape On The Landslide Stability In The Reservoir Environment

The Three Gorges area has high mountains,steep slopes and deep valleys.The geological conditions are very complex,becoming a landslide multiple areas in China.At present,there are thousands of old landslides in the reservoir area,and a part of them show some signs of revival after impoundment of the Three Gorges Reservoir,Wangjialiang landslide is just one of them.However,affected by the national and local financial constraints,some resurrection landslides of the Three Gorges reservoir area lack of survey data.Although few landslides have survey data,but the accuracy is very limited.The sliding surface shape of these landslides can be roughly inferred from experience.However,in the reservoir environment,the size of the floating load and the hydrodynamic pressure generated in the landslide are related not only to the rise and fall range of the water level,but also to the shape of the sliding surface.Therefore,it is of great practical significance to study the control effect of sliding surface morphology on the stability of reservoir landslide.This paper choose Wangjialiang landslide in Badong section of the Three Gorges Reservoir area as the object of study,and carry out the research on control of the sliding surface shape on the landslide stability in the reservoir environment.According to the material characteristics and the deformation status of Wang Jialiang landslide,it is inferred that the slip surface shape of Wangjialiang landslide is polygonal.Two types of sliding surfaces of two-fold linear and three-fold linear are determined.According to the length and angle of each segment of the sliding surface,16 kinds of sliding surfaces are subdivided.GeoStudio2007 software was used to analyze the variation trend of landslide stability with the change of the reservoir water level under different forms of sliding surface.The following informations are obtained:(1)Regardless of the shape of the slip surface,during the drawdown of reservoir water level,the groundwater level in the sliding body of Wang Jialiang landslide lags behind the water level of the reservoir,thus generating a hydrodynamic pressure in the slope.The greater the speed,the more obvious the hysteresis,and the greater the dynamic water pressure.During the rise of the reservoir water level,the groundwater level in the sliding body lags behind the rise of the reservoir water level,thus generating a hydrodynamic pressure in the slope.And the greater the speed of water level rise,the more obvious hysteresis,the greater the dynamic water pressure.The greater the speed,the more obvious the hysteresis,and the greater the dynamic water pressure.(2)When the sliding surface is the type of two section,during the process of the reservoir water level fluctuation,the stability of Wang Jialiang landslide is proportional to the length and proportion of the leading edge,and inversely proportional to the length and proportion of the trailing edge,and is proportional to the angle of the trailing edge.(3)When the sliding surface is the type of three section,during the process of the reservoir water level fluctuation,the stability of Wang Jialiang landslide is proportional to the length and proportion of the leading edge,and inversely proportional to the length and proportion of the middle part,and is proportional to the angle of the middle part,and is directly proportional to the length and angle of the trailing edge.(4)Comparing the stability of the two-stage slip surface with the stability of the three-stage sliding landslide,it is found that the stability of the two-stage sliding landslide is worse than that of the three-stage.(5)The deformation status of Wang Jialiang landslide shows that the landslide is basically stable,thus its stability coefficient Fs is greater than 1.05 and less than 1.10.In the process of reservoir water level fluctuation,there are four schemes meeting the conditions,that is,the minimum stability coefficient of landslide is between 1.05-1.10:(1)two-stage sliding surface-the trailing edgeangle of 35°;(2)three-stage sliding surface-the trailing edge angle of 70°-length of 8m-the middle section angle of 35°;(3)three-stage sliding surface-the trailing edge angle of 70°-length of 30m-the middle section angle of 25°.(4)three-stage sliding surface-the trailing edge angle of 70°-length of 30m-the middle section angle of 35°.It is speculated that the sliding surface shape of the landslide may be one of the four.