Research On Formation Mechanism And Stability Analysis Of Landslide In LeXi Expressway Conection Line Of Yonghong

Landslide is one of the main types of geological hazards in highway construction in mountainous areas in southwest China.The yonghong connecting line of the proposed lexi expressway is the main road leading to yonghong township of mabian county.Under the control of geological structure and rock mass structure and other factors,the geological hazards of landslides along the line develop and the genetic mechanism of landslides is complex.The proposed connection line crosses the landslide accumulation body in the form of excavation and filling subgrade for many times,which has an impact on the stability of the landslide and poses a potential threat to the construction and operation safety of the highway.Therefore,the evaluation of the stability of the landslide based on the study of the mechanism of landslide causes is of great practical significance in guiding the design of the proposed highway and ensuring the safety of the construction and operation of the highway.Find out the basic geological conditions of landslide is presented in this paper based on the basic characteristics and landslides,analyzes the influence factors of landslide formation and formation mechanism,analyses the present situation of the landslide stability evaluation and engineering stability under disturbances,the numerical simulation method analyzes the influence on seepage field and stability of the landslide is rainfall infiltration,and then puts forward Suggestions on the prevention and control measures.The following main research results have been obtained.(1)The landslide of the Yonghong connecting line is developed in a"chair-like"variable-inclination layered structure slope with a steep upward slope and a low slope.There are multiple landslides in the area,and the connecting line passes through five of them.Among them,the landslideⅠ-1 is in the shape of a"strip",the main sliding direction is 345°,and the volume is about 517.2 million m~3.The accumulation body of No.Ⅱ-1 landslide is in the shape of"ox yoke",the main sliding direction is gradually deflected from 6°to 320°,and the square volume is about 962.2 million m~3.The landslides No.Ⅰ-2,No.Ⅰ-3 and No.Ⅱ-4 are"long tongue-shaped"and belong to small and medium landslides.(2)Based on the analysis of landslide development characteristics and formation conditions,the formation mechanism and failure mode of the landslide were studied.Among them,the deformation and failure mode of No.-1 landslide changed from the"slip-pull"type developed in the early muddy interlayer along the bedding layer to the later"slip-bend"type;The mode is"slip-pull"type.3DEC discrete element numerical simulation software was used to reproduce the formation and evolution of the landslideⅠ-1 from the early"slip-pull"type to the later"slip-bend"type slope.The"buckling"position of type deformation failure is located at the trailing edge of the early landslide accumulation body.(3)On the basis of qualitative analysis,the limit equilibrium method was used to calculate and analyze the stability of the landslide under three conditions:natural,heavy rain and earthquake.The calculation results show that:Ⅰ-1 landslide is in a stable state under natural conditions,and the whole is basically in a stable state under heavy rain and earthquake conditions,and the local steep slope at the leading edge is under stable under heavy rain and earthquake conditions.TheⅡ-1 landslide is in a stable state under three operating conditions,and the central part of the steep slope is under-stable under heavy rain and earthquake conditions.The landslides No.Ⅰ-2,No.Ⅰ-3 and No.Ⅱ-4 are in a stable state under three working conditions.(4)Geo-studio numerical simulation analysis of the seepage field and stability change law of rainfall infiltration landslide,the simulation results show that:(1)Within a certain rainfall time,the greater the rainfall intensity,the greater the water content in the landslide accumulation body,the negative pore The lower the water pressure,the greater the groundwater level rise,and the worse the stability of the whole landslide and the local slope of the connecting line.(2)Under a certain rainfall intensity,the longer the rainfall duration,the greater the amount of rain infiltration,the smaller the matrix suction in the landslide accumulation body,the smaller the negative pore water pressure,the higher the groundwater level rise,and the worse the landslide stability.(3)Under a complete rainfall condition,after the rainfall stops,the pore water and surface water in the landslide accumulation body will continue to move to the deep part and the front edge of the landslide for a period of time,the negative pore water pressure in the accumulation body continues to decrease,and the stability continues to decrease.When the negative pore water pressure and stability decrease to the lowest value,the negative pore water pressure in the sliding body gradually rises,and the slope stability gradually increases.The restoration of pore water pressure in the landslide accumulation gradually developed from the surface to the deep.(5)On the basis of landslide formation mechanism and stability research,put forward specific prevention measures for landslides and subgrade slopes,and propose"surface drainage engineering+resistance"for larger landslidesⅠ-1 andⅡ-1"Slide pile supporting project+vegetation restoration+monitoring"prevention and control plan.