Study On The Complex Dynamic Effect And Stability Evolution Law Of The Accumulation Layer Landslides

In this paper,Shuping landslide,a typical accumulation layer landslide in the Three Gorges Reservoir area,is taken as the main research object.Firstly,according to the mechanism of rainfall infiltration,the weakening law of shear strength,elastic modulus and other parameters under different water content conditions are studied.The evolution law of seepage field,displacement field and stability of slope under different rainfall types are simulated and analyzed by Geostudio finite element software.The most dangerous rainfall conditions were obtained by comparative analysis of rainfall conditions.Secondly,the indirect composite analysis method is used to distribute the slope parameters in different regions during the rainfall process,and the evolution law of slope stability and displacement under the condition of the physical and mechanical parameters of rock and soil in different regions weakening during the rainfall process is analyzed and summarized.Finally,by comparing the accumulated displacement calculated by simulation under the condition that the parameters of rock and soil are not weakened and the zones are weakened with the real monitoring displacement,the theory that considering the physical and mechanical parameters of rock and soil can make the prediction time more accurate is verified.The research results are as follows:1.Under the condition of rainfall infiltration,with the increase of water content,the weakening rate of physical and mechanical parameters of rock and soil shows a trend of rapid increase first and then slow increase.According to the weakening rate,the weakening process can be roughly divided into three stages: the increasing stage of weakening speed,the slowing stage of weakening speed,and the setting stage of weakening speed.2.The weakening rate of rock and soil is related to the natural density of soil and the initial value of parameters.The larger the initial value of density or parameters,the greater the weakening rate.The weakening rate of cohesion is larger than that of internal friction angle,and the weakening rate of physical and mechanical parameters of clay is less than that of soil-rock mixture.3.According to the weakening rule of parameters and the initial value of Shuping landslide parameters,the average weakening rate of shear strength parameters and elastic modulus of the upper layer of Shuping landslide in the Three Gorges is obtained as follows: when the water content is between 11% and 20%,the average weakening rates of c,?and E are respectively 25%,23% and 45%;when the water content is between 21% and 30%,the average weakening rates of c,?and E are respectively44%,45% and 78%;when the water content is between 31% and full.The average weakening rates of c,?and E were 61%,55% and 86%,respectively.4.Under the condition of rainfall infiltration,the rock and soil on the surface of the slope are most sensitive to rainfall.With the rainfall,the surface layer of the slope first reaches saturation,and the water content of the slope does not increase linearly with the duration of rainfall and the increase of rainfall intensity,but there is a dissipation process after the water content reaches a certain value.The increasing speed of water content is in direct proportion to rainfall intensity and in inverse proportion to infiltration depth.5.When the total rainfall and rainfall time are fixed,four rainfall conditions are compared: rainfall concentration,rainfall reduction,rainfall average and rainfall increase.It can be seen that the slope stability coefficient is the smallest and the maximum displacement is the largest when the rainfall is concentrated.Therefore,the rainfall concentration is the most dangerous condition.6.Based on the study of displacement field and stability of slope under the condition of weakening and not weakening parameter zoning,it is found that the influence of weakening parameter zoning on slope stability and displacement mainly occurs in the middle and later period of rainfall.By comparing the accumulated displacement calculated by simulation under the condition of weakening and not weakening the parameter partition with the real monitored displacement,it is found that the accumulated displacement calculated by simulation under the condition of weakening the parameter partition is closer to the monitored displacement.Therefore,when predicting the instability time of slope,considering the weakening of geophysical and mechanical parameters can make the prediction time more accurate.