The Formative Mechanism And Slope Stability Analysis Of Wangjiagou Landslide In Guizhou Province

In July 14,2014,there was a ground fissure on the back side of Wangjiagou in Yinjiang Town,Tongren City,Guizhou Province.After five days of continuous heavy rainfall,landslides occurred in the early morning of July 18,2014.The landslide caused 28 houses to be damaged,108 of the 29 households were forced to migrate,and the direct economic loss was more than 3 million yuan.Landslide blocking slope below the river,endangering the safety of villages and towns downstream.Taking Wangjiagou landslides in Guizhou Province as the research object,combined with the Wangjiagou landslide investigation and engineering geological exploration,from the five aspects of topography,lithology,geological structure and earthquake,hydrological and geological conditions and human engineering activities on Wangjiagou landslide preliminary understanding.Then the formation mechanism of Wangjia gully landslide is analyzed through five aspects of geological structure,stratigraphic lithology,vegetation,rainfall infiltration,water rock physical action and water rock chemical action,and the stability of Wangjia gully landslide is judged in macroscopic view.This paper will analyze the stability of Wangjiagou landslide under two working conditions.First,the limit equilibrium method is used to calculate the stability coefficient of landslide according to the obtained section.Then the stability of landslide is calculated by numerical simulation.In this paper,before the numerical simulation,GOCAD software is used to build 3D geological body model,and then the CROSSSECTION function module of GOCAD software is used to intercept the section,and the intercepted section is calculated by FLAC^3D simulation stability.Based on the analysis of the formation mechanism and stability of Wangjiagou landslide,we can get the following conclusions:?1?The area is the deposit and its lower part of the Wangjiagou landslide.The main strata are landslides and silty siltstones composed of silty clay and clastic rocks.The physical and mechanical properties of the overlying soil layer and the lower rock stratum are very different.The interface is easy to form the weak structural surface,and the possibility of sliding of the landslide is very great;?2?The formation conditions of Wangjiagou landslide are analyzed from five aspects of topographic and stratigraphic and lithologic conditions,vegetation factors,rainfall infiltration,water rock physical action and water rock chemistry.It is believed that the unfavorable stratigraphic lithology and slope structure of the landslide provide a material basis for the formation of landslides,and the slope slope body is covered by a large number of plants and vegetation.The root action provides a channel for surface water infiltration and groundwater movement.After the continuous heavy rainfall,a large amount of rainwater is retained on the surface of the slope and infiltrated into the broken body,increasing the weight of the slide body,reducing the friction of the weak interlayer,reducing the physical and mechanical properties of the rock and soil,and underground water.The replacement of ions with rock and soil mass destroys the integrity of rock and soil;?3?The formation and evolution of the landslide can be divided into three stages:the river scour at the foot of the slope to form a steep ridge,and the slope surface irrigation makes the front of the landslide the first creep deformation;the rain is plentiful,the rainwater infiltration,the groundwater level uplift,over the soft clip layer,the overlying soil and the underlying rock strata,and the back edge of the landslide.With the increase of stress,the tensile cracks are formed,and the sliding surface is gradually formed.After continuous heavy rainfall,the slip surface is connected,the sliding body is started,and the landslide finally destroys;?4?Using the topographic map and borehole data of Wangjiagou landslide,the3D geological model is established by GOCAD software,and then the three dimensional model has been intercepted.The intercepted section is basically conformed to the landform characteristics of Wangjiaguo landslide.It is feasible to think that it is feasible to use the intercepted section for stability analysis;?5?The stability of Wangjiagou landslide accumulation stage is calculated and analyzed.The limit equilibrium method and the fast Lagrange finite difference method are adopted respectively.The results of limit equilibrium method show that the landslide is basically stable under natural conditions and is unstable under rainstorm conditions.The computed section of FLAC^3D is a section cut out by GOCAD.The results show that the Wangjiagou landslide is unstable under natural conditions and rainstorm conditions.The results obtained by the two methods are basically the same.It can be concluded that the Wangjiagou landslide accumulation body is in an unstable state.With the passage of time,or once again encountered extreme weather conditions,Wangjiagou landslide is likely to be damaged again,so it must be treated.