Analysis Of Deformation Mechanism And Stability Prediction Assessment Of Bazimen Landslide In The Three Gorges Reservoir Area,Zigui County

In this paper,Bazimen Landslide,a typical wading landslide in Zigui County of the Three Gorges Reservoir area,is selected as the research object.Based on the on-site supplementary investigation of landslide deformation monitoring data and comprehensive analysis of engineering geology,the typical section of landslide deformation is selected to establish the corresponding geomechanical model.The typical working conditions of landslide deformation are simulated by ABAQUS finite element analysis software,and the seepage field,stress field and displacement field are analyzed The deformation law,main influencing factors and failure mechanism of landslide are analyzed from the calculation results of field and plastic zone;the grey least squares support vector machine model established in this paper is realized by using MATLAB software to predict the deformation trend of landslide.On this basis,the deformation mechanism of landslide is analyzed,and the stability of landslide is comprehensively predicted and evaluated.The main conclusions are as follows:1.Bazimen Landslide is a typical chair like soil landslide.The slope is high in the West and low in the East,steep in the top and gentle in the bottom.It has a three-stage accumulation platform landform.The plane is irregular fan-shaped,the profile is stepped and concave,and the front edge reaches Xiangxi River,which provides a free surface for sliding.The sliding body is Quaternary loose accumulation rock and soil,which has the characteristics of loose structure,low strength,poor self stability and easy to soften in water.2.The cumulative displacement curve of Bazimen Landslide Deformation presents the characteristics of step change,and the deformation rate has a certain lag with rainfall and reservoir water level change period.The accumulated displacement changes greatly in several stages,which are after the reservoir water level drops and continue to the stable time of secondary water level.Compared with the numerical results,the landslide deformation is closely related to the decline of reservoir water level.3.The deformation of the back edge of Bazimen Landslide is mainly affected by rainfall,and the overall deformation is mainly affected by the decline of reservoir water level and the decline rate.The faster the decline rate of reservoir water level is,the more severe the landslide deformation is.The main factor of deformation restart is the effect of reservoir water storage on slope softening,which is mainly concentrated in the shallow layer of slope.Under the action of periodic regulation of reservoir water and long-term immersion softening,the sliding zone extends from the trailing edge to the middle and leading edge,and the deformation of the shallow surface of the leading edge leads to the displacement of the middle and the shallow surface of the trailing edge.4.The deformation mechanism of Bazimen Landslide is as follows: 1)soaking softening is reflected in the beginning of each stage of reservoir impoundment,part of the slope changes from the original semi saturated state to saturated state,and the matric suction and shear strength decrease after the clay particles are filled with water.Under the effect of reservoir water immersion,the physical and chemical softening action between water and soil increases the void ratio of some soil,reduces the cohesion and internal friction angle,further reduces the shear strength,and deforms under the combined action of self weight and external load of the slope;2)hydrodynamic pressure: when the reservoir water level rises or falls,the rise and fall rate of the groundwater level in the slope is lower than the change rate of the reservoir water level,and the shape of the slope is smaller When there is a certain head difference,the rise of the reservoir water level forms the reservoir water pressure of the back pressure slope,and the decline of the reservoir water level cancels the reservoir water pressure,but the decline of the groundwater level in the slope lags behind,and the downward hydrodynamic pressure is formed due to the head difference,which leads to the deformation of the slope.5.ABAQUS finite element analysis software and artificial intelligence glssvm prediction model are used to predict the stability of the landslide.The prediction results show that the landslide has the possibility of maintaining a long time creep state.(1)The numerical analysis results show that the Bazimen Landslide is in a stable state under the normal operation of the Three Gorges Reservoir area.The results show that:(1)when the reservoir water level rises rapidly and the rainstorm lasts for three days,the increase of the minimum tensile stress is 25.5%,the maximum displacement is 1911.0 mm,and the increase is 14.9%.(2)When the reservoir water level drops rapidly and the rainstorm acts together,the minimum tensile stress of the shallow layer of the landslide increases by 32.9%,and the maximum displacement of the landslide is 2757.0 mm,which increases by 44.3%.The plastic zone of the landslide expands more rapidly,but it is not completely connected at that time,and the whole landslide is still in a basically stable state.(2)The prediction results based on glssvm model show that: as of December 2021,the maximum deformation of Bazimen Landslide is located at the gsc2 monitoring point of the rear edge,and its cumulative displacement is 2313.4mm,and the cumulative monthly average displacement change is 30.2mm,while the minimum deformation of Bazimen Landslide is located at the gsc7 monitoring point of the middle,and its cumulative displacement is1187.1mm,and the cumulative monthly average displacement change is only 14.4mm.The analysis shows that the deformation of Bazimen Landslide still keeps the characteristic that the deformation of its rear edge is larger than that of its middle and front edge.Although the deformation of the landslide increases continuously,it still maintains in the creep deformation stage.