Study On The Seepage Field Characteristics And Stability Evolution Law Of Landslide Under Reservoir Fluctuation

The terrain difference in the Three Gorges Reservoir area is very large,which is significantly affected by reservoir water level,rainfall and other factors.It's a typical area with high incidence of geological hazards in China,where many landslides with strong disaster and great influence are produced.Due to the need of the Three Gorges Project,the reservoir water level in the Three Gorges area of the Yangtze River has to undergo periodic fluctuation of high water level every year,which has a great influence on surrounding reservoir bank landslide.The seepage field of reservoir bank landslide is prone to dynamic changes caused by reservoir water level,which leads to the destruction of the original balance in the slope and further affects the stability of the landslide.Therefore,taking the typical reservoir bank accumulation landslide-Bazimen landslide in the Three Gorges Reservoir area as the research object,the ratio k/v of slope saturated permeability coefficient k to reservoir water level fluctuation rate v was selected as the main control parameter of slope seepage field,and the influence law of different k/v on slope seepage field under the condition of reservoir water level fluctuation was analyzed.At the same time,the variation law of displacement field and stability of landslide under different k/v conditions was studied by using Geo-Studio finite element simulation software.On this basis,the variation law of the stability coefficient of different k/v type landslide under the simplified actual reservoir water level operation scheme was analyzed,and the optimization and adjustment suggestions were put forward for the existing reservoir water level operation scheme.The main research results are as follows.(1)In the stage of reservoir water level fluctuation,the shape of infiltration line was different under different k/v conditions.According to the shape characteristics of infiltration line,landslides can be divided into three types: k/v>10,10?k/v<1 and k/v?1:when k/v>10,the shape of infiltration line is horizontal straight line or slightly inclined straight line;when 10?k/v<1,the shape of infiltration line is inclined straight line;when k/v?1,the shape of infiltration line is curve.The difference between the angle of each infiltration line at the slope and the angle at the bedrock was selected as a parameter to quantitatively describe the characteristics of infiltration line at the end of reservoir water level fluctuation.It was found that whether the reservoir water level rises or falls,the?S is negatively correlated with k/v overall.(2)The variation characteristics of seepage field of slope under different k/v conditions were analyzed by using the SEEP module of Geo-Studio software,and the following analysis results were obtained:(1)In the process of reservoir water level fluctuation,the maximum unit flow of seepage field is positively correlated with the rise and fall rate of reservoir water level and the permeability coefficient of slope.(2)In the process of reservoir water fluctuation,the change of groundwater in slope is positively correlated with k/v.(3)In the rising stage of reservoir water level,the pore water pressure of slope is positively correlated with k/v;in the falling stage,the pore water pressure is negatively correlated with k/v.(3)During the process of reservoir water level fluctuation,the evolution law of displacement field and stability of accumulation landslide under different k/v conditions were analyzed.The evolution law of the stability of different k/v type landslide were determined as follows:(1)When k/v>10,the stability coefficient of landslide decreases in the process of reservoir water level rising,and increases in the process of reservoir water level falling.(2)When 10?k/v<1,the stability coefficient of landslide decreases in the process of reservoir water level rising,and decreases first and then increases in the process of reservoir water level falling.(3)When k/v?1,the stability coefficient of landslide increases in the process of reservoir water level rising,and decreases in the process of reservoir water level falling.(4)The mathematical expression of the relationship between the slope stability coefficient and k/v was established by Origin software,and it was found that the slope stability is negatively correlated with k/v in the rising stage of reservoir water level,and positively correlated with k/v in the falling stage of reservoir water level.Combining the seepage field and stability of landslide,the mathematical expression of the stability coefficient of landslide and characteristic parameters of seepage field was determined.It was found that the slope stability is positively correlated with the angle in the rising stage of reservoir water level,and negatively correlated with the angle in the falling stage of water level.(5)According to the actual operation of reservoir water level in the Three Gorges Reservoir area,the actual operation scheme of reservoir water level was simplified,and the variation law of landslide stability with different k/v types under the actual simplified scheme was studied.Based on the actual operation requirements of reservoir water level and the variation law of landslide stability,the optimization and adjustment suggestions for water level dispatching in Three Gorges Reservoir area were put forward.