Research On The Revival Mechanism Of Shiziyuan Landslide On Jiangxi Expressway And Its Governance Project Effect Evaluation

Due to the complicated geological conditions in southwest China,slope excavation is inevitable due to the limitation of terrain during highway construction,which results in deformation and failure of slope.The landslide disaster has become an important factor that restricts the construction of highway engineering and has caused serious harm to the construction and operation of highway.The Shiziyuan Landslide is located in JK64+280～JK64+580 section of Jiangxi Expressway.The landslide was affected by excavation and showed obvious signs of deformation and resurrection,therefore,the emergency treatment of the landslide is based on anti-slide pile.It is of great significance to ensure the safe operation of highway,and it is also of certain reference value to the study on the deformation mechanism and treatment of similar highway landslides.Based on the investigation of geological engineering conditions and structural characteristics of landslide,the genesis mechanism of ancient landslide is analyzed by the method of geology-mechanics.By means of geological analysis and numerical simulation,the mechanism of landslide revival under highway excavation and heavy rain is studied.Using a combination of qualitative and quantitative methods to evaluate the overall and local stability of the landslide.According to the implemented treatment projects,the landslide body displacement monitoring data analysis,numerical simulation and fuzzy mathematical theory are used to evaluate the effects of the treatment projects.The research results are as follows.(1)The slope in the study area is a gentle slope with outer structure composed of interbedded sand and mudstone,The deformation failure mode of ancient landslides is slip-crack type。The soft intercalation of silty clay formed by mudstone intercalation constitutes the sliding surface(zone)of sliding and tensile failure.(2)Excavation is the main factor leading to the local revival of the landslide,and rainfall further promotes the deformation and failure of the landslide.When the excavation depth is about 4m(at an elevation of 880m),a large number of tensile cracks began to appear in the ancient landslide at an elevation of 889～891m on the trailing edge of the excavation slope.At 6.5m(877m elevation),the deformation of the landslide further developed backward to an elevation of 901 m,forming the current deformation zone.(3)The Midas/GTS is used to simulate the stress,displacement,plastic deformation zone and shear strain increment of the landslide in the unexcavated and excavated conditions under natural and rain conditions.The simulation results show that after excavation,the stress field of the slope body changes,the displacement gradually increases,the plastic deformation and plastic failure range increase,and the shear strain increment penetration area basically penetrates the entire deformation zone.(4)Use the transfer coefficient method to analyze the overall and local stability of the landslide.The calculation results show that:after the highway is excavated,the whole landslide is in a stable state in the natural state and basically stable in the rainstorm state,and the deformation zone of the front edge of the landslide is in the unstable state in the natural state and unstable in the rainstorm state.(5)Based on the analysis of the internal displacement data and the simulation of the distribution characteristics of the slope position and shear plastic zone after the completion of the landslide treatment project in Simziyuan,the effect of the treatment project has been evaluated,which shows that the retaining structure is effective.(6)The comprehensive evaluation model of treatment effect was established by using fuzzy mathematics theory,and the evaluation results were divided into four grades: excellent,good,general and poor.According to the actual engineering situation of shiziyuan landslide,a total of 10 evaluation factors are selected.After determining the weight of the evaluation factors,the shiziyuan landslide treatment effect is determined to be good according to the principle of maximum subordination.