Study On The Mechanism Of Deformation And Failure And Stability Of The Xiaowan Landslide Group In Yunnan Province

Landslide is one of the common geological hazards in China.China has a vast territory,and the geological conditions vary widely throughout the country.Xiaowan town of Yunnan province is located on the Yunnan Guizhou Plateau.The geological structure and the structure of the rock and soil are complex.The research on the mechanism of deformation and failure and stability of Xiaowan landslide group can provide some reference for the local disaster prevention and reduction.Based on reconnaissance,geotechnical test,engineering geological analysis,transfer coefficient method and strength reduction finite element numerical simulation,this paper conducts a comprehensive study of landslide in Xiaowan landslide group.The main conclusions are as follows:(1)The Xiaowan landslide group consists of 4 landslides(H1,H2,H3,H4).This paper classifies the landslides from 4 aspects.The main causes and inducing factors of landslides in the study area are analyzed.The failure modes of Xiaowan landslide group are translational-traction type(H2,H3,H4)and traction type(H1).The formation mechanism is the creep-rupture mode,and the slide surface areas of all the landslides are not completely connected.The deformation and failure of the landslides in the study area must pass through these three stages: stage I(Creeping-tractive cracks forming),stage II(Cracks expanding-the back edge tension forming),stage III(slide surface areas connecting-landslide holistic slipping).The landslide H2,H3 and H4 are at stage II,and the landslide H1 is at stage I.The comprehensive analysis shows that the whole slope zone which the landslide group located in is in a state of instability.(2)The shear strength parameters of potential sliding surface I and potential sliding surface II are obtained by "experimental method + artificial stratification statistics".It is shown that the shear strength test parameters of the soil layer near the potential sliding surface can represent the shear strength parameters of the sliding surface.The typical landslide H2 can adopt the test parameters of the shear strength,which proves that this method can be used to evaluate the stability of the landslide in the study area or the local type landslides.(3)Based on the transfer coefficient method,a single factor method is used to analyze the sensitivity of landslide parameters.Under natural,rainstorm and earthquake conditions,the sensitivity of the internal friction angle is greater than that of cohesive force C.(4)First of all,through engineering geological analysis,we determine 2 potential sliding surfaces of landslide: I and II.Then taking typical landslide(H2)as an example,transfer coefficient method and strength reduction finite element method are used to analyze respectively.It is proved that the applicability of transfer coefficient method and strength reduction finite element method in solving multi potential sliding surface landslides.Under the natural,rainstorm and earthquake conditions,the results of the two calculation methods are consistent.That is,under the natural condition,the H2 landslide is basically stable,and the H2 landslide is in the unstable state under the rainstorm and earthquake conditions.The transfer coefficient method is consistent with the strength reduction finite element method in determining the position of the sliding surface.the position is the potential sliding surface II.The transfer coefficient method is a special case in this case,This method does not apply to the stability calculation of all the creep-rupture type landslides with multi potential sliding surface and the slip surface is not through.and the strength reduction method is more universally applicable.(5)In the numerical simulation,by observing the effective plastic strain diagram under different working conditions,the green effective plastic strain zone(plastic zone)is expanded to reveal that the failure mechanism of H2 landslide is the translational-traction mode.