Analysis Of Rainfall Seepage And Stability Of Large Slip-Type Deposit Body

The deep landslide induced by rainfall is generally divided into deposit body landslide and bedrock type landslide.According to statistics,the rainfall-induced deep landslide,the slippery body from clay,fragments of stone soil,such as the formation of landslides easily occur,accounting for more than 90%,this type of landslide is generally a deposit body landslide.The sliding body is difficult to slide from the slope of hard rock such as sandstone and shale,and this kind of landslide is usually bedrock type landslide.The sliding body of the stacked body landslide has the characteristics of high porosity,high permeability and easy flow.Under the condition of strong rainfall,it is easy to slide along the weak structure surface or rock stratum weathering and crushing,the depth range of sliding body is dozens of meters to hundreds of meters,and it has the characteristics of large area,high speed and wide destruction range,and its own and secondary effect will give people life safety,Property poses a major threat.Therefore,it is of theoretical and practical significance to study the rainfall seepage and stability analysis of large slip-type accumulation body in landslide control work.In this paper,the geological environment and the basic characteristics of Cai Jia Ba slip-type deposit body are analyzed deeply by taking large slip-type pile as the research object.The soil-water characteristic curve of the soil in situ sampling is determined by using a transient water-holding and suction device(trim instrument).Finally,the Geostudio software is used to simulate the Cai Jia Ba slip-type stacking body,and the following research results are obtained:(1)Theoretical study on saturated-unsaturated seepage flow under rainfall.The continuity equation of seepage flow can be obtained by applying the principle of mass conservation to the flow of fluid in porous media.By combining Darcy's law with continuity equation,the differential equation and the definite solution condition of unsaturated seepage are obtained,which can be used as the basis of numerical simulation.(2)Based on the analysis of the natural geographical environment,topography,geological conditions,landslide characteristics and material composition of landslide in Cai Jia Ba landslide,it is concluded that the Cai Jia Ba landslide is divided into the deposit body sliding and rock mass sliding,and the sliding of the stacking layer is characteristic of sliding,and the rock sliding has the characteristics of flat pushing.The landslide of Cai Jia Ba slip type is a compound landslide,such as the revival of ancient landslide,the slip of weak basement and the revival of shallow slide.(3)The soil-water characteristic curve of the soil in situ sampling is determined by using the transient water-retaining and water absorbing device(trim instrument),the soilwater characteristic curve curve in the condition of moisture removal and hygroscopic is only coincident when the volumetric water content is less than the residual water content,and in other cases,the matric suction in the desorption state is greater than the matric suction of hygroscopic state.There is a lag effect.The permeability coefficient curve also has hysteresis effect.(4)The soil-water characteristic curve of the soil in situ sampling is determined by using the transient water-retaining and water absorbing device(trim instrument),the soilwater characteristic curve curve in the condition of moisture removal and hygroscopic is only coincident when the volumetric water content is less than the residual water content,and in other cases,the matric suction in the desorption state is greater than the matric suction of hygroscopic state.There is a lag effect.The permeability coefficient curve also has hysteresis effect.(5)By coupling the SEEP/W module with the slope/w module,the seep/w seepage result and the unsaturated shear strength theory are combined,and the limit equilibrium method is used to analyze the influence of different rainfall intensity and rainfall holding on the slope stability.It is found that the higher the rainfall intensity,the longer the duration,the higher the slope safety factor decreases,and the minimum safety factor is not the rain stop time,but the time after the rain stops.(6)Combined with the rainfall data of the Cai Jia Ba landslide in August 2014,the Geostudio software seep/w,slope/w and SIGMA/W modules were used to study the seepage field,stability,stress field and displacement field.It is found that under the action of rainfall,the volumetric water content,pore water pressure,effective stress,safety factor and displacement deformation of the sliding body are the larger the rainfall,the greater the absolute value of these values,all of which have hysteresis effect,all are the absolute values of the bottom change of the slope are greater than the top The maximum shear stress appears in the mud steep ridge,sand mudstone contact surface,these areas under the strong rainfall conditions,the upper part of the sliding surface has reached the limit shear strength,the leading edge has the temporary void condition,easy to follow the weak structural surface to occur the whole or the partial landslide.With slip-type characteristics.