Stability Analysis And Control Measures Optimization Of A Landslide In Weiwu Expressway

Landslide is one of the three major geological hazards in China.It is most common in Northwest China.It extensively affects the safety of personnel and property in the construction and operation of railways,highways,and more and more scholars in the industry pay attention to it.In the landslide remediation project,because of the insufficient geological survey work,survey technology and survey data in the early stage,the cause and mechanism of landslide formation are not well understood,which leads to the failure of the design of the later stage remediation.In addition,in the process of determining the landslide treatment scheme and selecting the relevant treatment parameters,the designer usually only compares the existing projects and adjusts the calculation according to the requirements of the codes.The matching is poor in the actual engineering application process,and the design results tend to be safe,which often results in great waste.Therefore,how to thoroughly study the geological survey data,understand the causes and mechanism of landslide formation,carry out the analysis of landslide thrust and stability,optimize the design of landslide treatment scheme,and formulate economic and reasonable remediation measures has become a problem worthy of in-depth discussion.In view of the above problems,this paper relies on the Shiezi Landslide Treatment Project of Weiwu Expressway as the background,takes the optimization of the treatment scheme as the ultimate goal,and uses the methods of comparison,control variable,limit equilibrium and Abaqus finite element strength reduction to explore the landslide as follows:?1?According to the comprehensive survey data,the causes and formation mechanism of landslide are analyzed in depth.The landslide's geotechnical structure is a special"two clamps"structure.The upper layer is a loose slope collapse layer?strong permeable layer?,the lower layer is alluvium,and the two layer is sandwiched with cohesive soil about 20cm.The excavation of slope toe is the fundamental factor for the formation of landslides,and spring melt rain?snow?water infiltration is the inducing factor.?2?The stability of three sections of the landslide under two working conditions?natural and rainfall?is calculated by transfer coefficient method.The results show that under natural conditions,the three profiles are in an unstable-basically stable state,and under rainfall conditions,the three profiles are in an unstable state.The landslide thrust of the three sections of the landslide is analyzed and calculated.The results show that the landslide thrust is 3888.78 kN,2696.57 kN and 951.05 kN.?3?Based on Abaqus finite element strength reduction method,a two-dimensional model is established:?1?The stability of the landslide and the deformation characteristics of the slope are analyzed.The calculated results show that the landslide is in an unstable state,which is consistent with the theoretical calculation.?2?The horizontal displacement of each point on the four paths of A-B,C-D,E-F and G-H is extracted.The abrupt change of horizontal displacement is the location of the slip surface.A method for determining the slip surface is put forward,which can be used as supplement and verification of geological data.?3?The influence of different factors?external and internal?on the stability of the landslide and the location of the slip surface is analyzed.The results show that:1)The slip soil has the greatest influence on the stability of the landslide,followed by the slip zone soil,and the slip bed soil is the smallest;the location of the slip surface does not change with the change of the soil layer.2)The change of shear strength parameters c and?will form a weak layer,which has the greatest influence on the stability of the landslide,and the position of the slip surface will shift to the weak layer.3)The change of E and?only affects the deformation of landslide,but does not affect the stability of landslide and the location of sliding surface.4)Rainfall,excavation at the foot of slope,earthquake and so on will reduce the stability of slope.?4?Based on Abaqus finite element strength reduction method,a three-dimensional model is established:?1?The influence of pile position,pile spacing?soil arching effect?and anchorage depth on the reinforcement effect of single row anti-slide piles in the process of slope reinforcement is explored.The results show that the optimum pile position is near the middle of the slope.The pile spacing is S/D=2-6,so the soil arching effect can be effectively exerted.The best anchorage depth is 0.4-0.5Lp.?2?The influence of pile position and row spacing of double-row anti-slide piles on reinforcement effect is explored.The results show that the optimum pile position is near the middle of the slope.The row spacing should be greater than the critical row spacing X_min,and the row spacing X?X_min,so that the back row piles have no shielding effect on the front row piles,and the reinforcement effect of the front row piles can be brought into full play.?3?On the basis of the above research results,two treatment schemes are formulated?cutting side+single row anti-slide pile,cutting side+double row anti-slide pile?.The feasibility and economy of the two governance schemes are optimized and compared.Finally,the second one is chosen as the governance scheme.