Study On Stability Of The Slope Along The Three Gorges Reservoir Under The Action Of Reservoir Water Level Change And Rainfall

Geological hazards are very well developed in China,among which the landslide has become a type of geological hazards that cannot be ignored due to its frequent occurrence and huge disaster losses.Since the operation of the Three Gorges reservoir,hundreds of landslides have been detected around the reservoir,and more than 5,000 potential landslides have been detected.The wading landslide seriously endangers the life and property safety of fishermen and people on the bank of the reservoir.It is of great practical significance to study the stability of the slope along the bank of the reservoir.The landslide along the Three Gorges is affected by many factors.With the help of Seep/W module and Slope/W module of geo-studio software,the influence of variation of reservoir water level and rainfall conditions on slope seepage field and its stability was studied,and suggestions were put forward for water level scheduling in the reservoir area.The sensitivity analysis of single factor and multi-factor combination of factors affecting the slope stability was carried out.The main research contents and achievements are as follows:(1)The seepage field and stability of the slope are analyzed when the water level of the reservoir is raised and fall,and the rising and falling rates of the three types of reservoir water and the permeability coefficient of the rock and soil of the bank slope are taken as variables.The results showed that the higher the water level rising speed or the lower the slope permeability coefficient,the more concave the infiltration line shape will present inside the slope,the greater the water level difference inside and outside the slope,and the larger the stability coefficient will present.The larger the water level drop rate or the smaller the slope permeability coefficient,the more prominent the slope infiltration line shape will present.The larger the water level difference inside and outside the slope,the smaller the stability coefficient will present.(2)The seepage field and stability of slope under rainfall condition are analyzed,and three different rainfall intensity and duration are taken as variables.The results show that the larger the rainfall intensity or the longer the rainfall duration is,the larger the saturated area inside the slope will exist,the larger the pore water pressure will be affected and the smaller the stability coefficient will be.(3)By analyzing the seepage field and stability of the slope when the water level rises or falls in combination with rainfall,it is found that the slope stability will be reduced by the effect of coupled rainfall whether the water level rises or falls.(4)In order to obtain the sensitivity degree of the slope stability to each influencing factor,the single factor and multi-factor orthogonal analysis method in the sensitivity analysis were used to carry out the single factor sensitivity analysis and multi-factor orthogonal analysis respectively on the factors influencing the slope stability,and the two algorithms were integrated.The single-factor analysis method and the variance analysis method proved that when water level rose,the slope permeability coefficient was the most significant factor affecting the slope stability.According to the range analysis method in the orthogonal test,the sensitivity of slope stability to various factors when water level rises is ranked as follows: slope permeability coefficient,water level rising speed,rainfall duration and rainfall intensity.When the water level drops,the sensitivity of the slope to each factor is ranked as follows: slope permeability coefficient,water level falling speed,rainfall intensity and rainfall duration.(5)Based on the above research and the case study of the wading landslide project in the Three Gorges reservoir area,the changes of the landslide stability of the rising water level,rainfall and actual failure state(rising water level coupled with rainfall)are calculated,and the comparative analysis is made,verified the rising water and rainfall coupling can reduce the slope stability,finally caused the landslide.