Study On The Stability Of Landslide Accumulation Under Large-Scale Excavation

Landslides occur frequently in China,which seriously threaten the safety of human life and property.Human engineering excavation has induced a large number of landslide geological disasters,especially the excavation on the accumulation body will inevitably affect its stability.Therefore,the control of large-scale excavation is an important engineering problem.In this paper,through Abaqus finite element numerical simulation,the excavation of accumulations with different deposit-bedding interface forms is studied,and the influence of excavation conditions and excavation procedures on the stability of accumulations with different deposit-bedding interface forms is also explored.Taking the ancient landslide accumulation of a project site as an example,the deformation evolution mechanism and stability of its original slope are studied.And through the comparative analysis of different excavation plans to optimize the excavation plan.The main works and conclusions of this study are as follows:(1)Two landslide models having linear and chair deposit-bedding interface are proposed.The excavation position,the width of the excavation platform,the excavation Angle and the vertical height of the adjacent excavation platform are the controlling factors of excavation.The influence of these excavation factors on the stability of landslide accumulation body with two types of deposit-bedding interface morphology is studied.And clearly defined good and bad excavation plans.Adoptting grey correlation method(one analysis approach)excavation control factors are ranked as follows according to influence:(1)linear:L>ΔH>ΔS>θ;(2)chair:ΔS>L>θ>ΔH.(2)Through three-dimensional numerical simulation analysis,the influence of excavation process on the stability of two types of deposit-bedding interface accumulation body is studied.Take the four excavation processes of parallel groove hopping excavation,stepped excavation,parallel sequential excavation and block parallel excavation as examples.The displacement,plastic distribution and safety factor during the excavation process of the landslide accumulation in each excavation scheme are compared and analyzed.According to the calculation results,when large-scale excavation is carried out,the landslide deposits with linear deposit-bedding interface are excavated from the middle and upper part of the slope,and the parallel groove hopping excavation scheme is preferred.The landslide deposits with chair deposit-bedding interface are excavated from the top of the slope,and the excavation scheme combining parallel groove hopping and stepped excavation is preferred.(3)The deformation evolution mechanism and stability of the ancient landslide accumulation body at a project site were studied by numerical simulation.The ancient landslide accumulation is in a stable state in the natural state.Only steep terrain is prone to local slump under heavy rain conditions.So,it can be used as a large-scale construction site.In case of instability failure,the failure mode may be slip-pull cracking in the upper-middle parts and creep-pull cracking in the lower-middle parts of the accumulation,and finally form traction sliding failure.Through the analysis of the excavation stability of the ancient landslide accumulation under the two excavation schemes,it can be seen that the accumulation may be sheared and damaged at the front edge of the slope after excavation,and the stability of the slope is greatly reduced.The excavation optimization scheme of the parallel groove hopping can effectively reduce the displacement and deformation of the slope during the excavation process,and greatly improve the stability of the slope.