Analysis Of Deformation Mechanism And Potential Surge Risk Of Soil Landslides With Stepwise In ZiGui Country Three Gorges Reservoir

Stability of landslides and potential surge hazards in the Three Gorges Reservoir area are the key research fields for geological experts and scholars.Zigui county is located in the Three Gorges Reservoir area.Since the impoundment,many landslides have become more and more active,threatening the safety of people's lives and property in the reservoir area.Large scale wading landslides once entering into the water at high speed,which not only threatens the people along the river,but also may affect the stability of the Three Gorges dam,once it crosses the dam crest,it even affects the downstream people.Therefore,it's of great significance to analyze the potential surge disaster of landslides.Combined with the monitoring data for many years,landslides with obvious step type characteristics is determined from 38 landslides monitored in Zigui County,and the characteristics and commonness of this kind of landslides are explored from the displacement change map;Through the simulation analysis of the stability of typical step landslide by GeoStudio software,these landslides stability characteristics of Bazimen landslide and Heishiban landslide are analyzed under the actual reservoir water level change from 2007 to 2019.Using slice method to calculate potential maximum sliding velocity.Using the formula method and survey software to analysis the maximum potential first wave height,the maximum surge climb on the other bank,the wave height along the river course and the influence range and extent of the surge.The conclusion is as follows.(1)Among the 8 step landslides,there are 4 overall step deformations:Bazimen landslide,Baijiabao landslide,Baishuihe landslide,Tanjiawan landslide;There are 4 local step deformations:Heishiban landslide,Sanmendong landslide,Shuping landslide,Woshaxi landslide,all of these landslides are all composed of clay and gravel.(2)Under the periodic change of reservoir water level,the stability coefficient of Bazimen Landslide increases with the decrease of reservoir water level,while the stability coefficient of Heishiban landslide decreases with the increase of reservoir water level;Bazimen Landslide belongs to the type of water recession lag landslide,which is in an unstable state.And it potential maximum sliding velocity is 4.94m/s;Heishiban belongs to the landslide of water storage lag type,which is basically stable,and the potential maximum velocity is 5.77m/s.(3)According to the formula method,the first wave height of potential surge of Bazimen Landslide is 7.27 m and heishiban landslide is 9.79 m under 175 m reservoir water level;The maximum climbing height on the opposite bank of Bazimen Landslide is 22.59 m,Heishiban landslide is 30.42m;The influence range of the surging wave of Bazimen Landslide is about 45 km,and that of heishiban landslide is 17.6 km;Under the water level of 145 m,potential surge influence of Bazimen Landslide is greater than that of 175 m,and Heishiban landslide is smaller.(4)Compared with the results of formula method and numerical simulation,the former calculated surge influence value is larger.The potential surge of Heishiban landslide will affect the main channel navigates of the Yangtze River at 175 m reservoir level,but not at 145 m.The potential surge of the both landslides will not affect the Three Gorges dam.