Analysis Of Landslide Stability And Prevention Measures In The Central School Of Mashu Town

The environmental conditions of landslides in Yunnan are very complex,and their complexity is reflected in the fact that landslides are often influenced by more than one triggering effect,such as the combined effects of human engineering activities(e.g.excavation),earthquakes and rainfall.At present,there has been a great deal of research on the formation mechanism,stability evaluation and prevention of landslides under the action of single triggering factors,but further research is still worthwhile on the combination of triggering factors,stability evolution and effective prevention of landslides under complex environmental conditions.The paper takes a typical landslide in the earthquake zone of Yunnan Province,the landslide of the central school in Ma Shu Town,Qiaojia County,Zhaotong,as an example.Based on the detailed investigation and data acquisition of the example,the paper integrates the techniques of rigid body limit equilibrium and numerical simulation to study the evolution process and law of the stability of the landslide under the progressively complex triggering conditions in accordance with the actual sequence of the emergence of the triggering factors,thereby revealing the contribution of different triggering factors to the reduction of the stability of the landslide The study will reveal the contribution of different triggering factors to landslide stability reduction,their role and combined effects.On the basis of this,the formation mechanism of these landslides will be elucidated,and effective countermeasures for landslide prevention and control will be explored by combining the theory of landslide prevention and control with years of practical experience through scenario comparison analysis.The thesis can provide a reference for the evaluation and control of landslides in complex environmental conditions.The main conclusions are as follows:(1)The landslide of Mashu Town Central School is about 165m wide in transverse direction and 65m long in longitudinal direction.The plane shape is in the shape of an armchair.The sliding direction of the landslide is consistent with the slope direction of the slope.The main sliding direction is 156°.The landslide area is about 8040m~2,the thickness of the landslide body is 7.0～15.0m,the average thickness is about 10.0m and the volume is about 8.04×10~4m~3,A small medium level traction soil slide.The topography and the lithological structure of the slope are the basic conditions for the formation of this landslide.Excavation disturbance and earthquake seismicity are important factors in the formation of this landslide,while continuous rainfall after the earthquake is the direct cause of the landslide.(2)Under three different stages,three typical sections of the landslide were selected and stability calculations were carried out using four classical mechanical methods such as the Swedish strip division method,the Bishop method,the simple cloth method and the transfer coefficient method combined with finite element simulations,respectively,and the results showed that:(1).The stability coefficients of three different landslide profiles in all three phases are:natural condition>earthquake condition>post-earthquake storm condition,and profile 1 is the most stable,profile 2 is the second most stable,and profile 3 is the worst;(2).The contribution of different triggering factors to landslide stability reduction is post-earthquake rainstorm>earthquake>self-weight,and the combined effect of earthquake and rainstorm triggering factors has a significant increase effect on landslide damage contribution;(3).The higher the overall stability of the slope,the lower the overall maximum principal stress of the slope.In the natural condition,the slope is in a stable state;in the seismic condition,the slope is in a basically stable state,but the local slope surface has started to produce creeping deformation;in the post-earthquake storm condition,the slope is in an unstable state,and the landslide needs to be managed in time.(3)Numerical simulation studies reveal that the mechanism of landslide formation under complex environmental conditions is:under natural conditions,earthquakes generate horizontal seismic forces,which increase the sliding force of the landslide body and reduce the effective stress at the same time,slowly deforming the leading edge of the slope body and pulling the geotechnical body in the middle of the slope body to deform,resulting in local deformation and displacement of the slope body and reducing the stability of the landslide;after the earthquake,the geotechnical structure is disturbed,and coupled with the influence of heavy rainfall,the cohesion and internal friction angle in the soil layer are reduced,the infiltration force increases and the sliding force increases,resulting in a landslide.(4)According to the results of the analysis of the causes and stability of the landslide in Ma Shu Town Centre School of Qiaojia County,combined with the principles of landslide management measures,two different landslide management schemes were proposed,and after a comparative study of the two landslide management schemes with different influencing factors,Scheme 1 was obtained as the best choice,and the specific reinforcement measures were:anti-slip piles+chipping works+slope protection works+interception and drainage works.(5)On the basis of the research on the stability and management of landslides at different stages of the Ma Shu Town Centre School,effective countermeasures against landslides under complex environmental conditions are further proposed:for slopes in excavation conditions only,cutting and counterpressure works are often used for management.For landslides in seismic conditions,support and retaining works(such as anti-slip piles and retaining walls)are often used.For slopes in rainfall conditions,interception and drainage works+slope protection works are often used.For slopes in post-earthquake rainstorm conditions,a comprehensive management plan of anchoring works(such as anchor cables(rods)and frame beams)+cutting works+slope protection works+interception and drainage works should be adopted.