Study On Soil Arching Effect And Landslide Thrust Of Anti Slide Piles In Reservoir Bank Landslides

The fluctuation of water level in the Three Gorges Reservoir Area will form a vertical height of up to 30 meters along the reservoir bank,and a large number of landslide control anti-skid pile projects in the accumulation layer will be affected by the fluctuation zone.The mechanical properties of the soil around the pile will continue to deteriorate due to the fluctuation of water level in the reservoir,leading to the loss or even destruction of the soil arch effect caused by the interaction between the landslide and the anti-skid pile,which has become a bottleneck problem affecting the long-term stability of landslide control in the Three Gorges Reservoir Area.Based on the Shilongmen landslide in Dazhou Town,Wanzhou District,Chongqing,the Three Gorges Reservoir area,this paper designs and makes a physical model of the landslide using the similarity principle;Obtain indoor and on-site monitoring information on soil pressure,displacement,pore water pressure,and anti slip pile strain of landslide soil before and after piles,and explore the relationship between soil strength parameters,landslide thrust,and soil arching effect.Based on numerical simulation to reproduce the experimental process,the relationship between soil arching effect and landslide thrust under the action of water level fluctuations is revealed.A soil arching effect failure criterion model considering changes in landslide thrust and weakening of soil parameters is constructed.The research results provide a theoretical basis for the long-term stability evaluation of landslide treatment in the accumulation layer of the reservoir bank.Based on the research content of the paper,the following research results have been achieved:(1)By observing the macroscopic deformation signs of slope,it is found that the main deformation characteristics of landslide under the combined working condition of reservoir water level fluctuation and landslide thrust include slope erosion,slope deformation and crack,slope instability and slide.Due to the effects of water erosion softening and osmotic pressure,the strength parameters of sliding soil are constantly weakened,cracks appear in the soil,and soil arch effect results in loss and damage,which directly affects the supporting effect of anti-sliding pile.When the soil arch effect is lost,the soil behind and between piles will slip.(2)Through the information monitoring and analysis of the internal deformation and failure mechanism of the slope,it is found that the water content and pore water pressure of the slope are changed by the fluctuation of the reservoir water level,and the internal friction Angle and cohesion of the soil are weakened,thus weakening the strength parameters of the landslide soil mass and pile-soil contact zone.Under the combined condition of reservoir water level fluctuation and landslide thrust,the stress of anti-slide pile in the middle of slope is greater,and the existence of side pile effectively eliminates the boundary effect problem.Therefore,the anti-slide pile in the middle of slope produces crack damage,and finally affects the equilibrium condition of soil arch effect,showing different degrees of soil arch effect loss and damage.The influence on the leading edge soil and the soil between the antislide piles is more direct.When the thrust exceeds the ultimate resistance of the anti-slide pile,the anti-slide pile body cracks and destroys the soil arch balance condition,resulting in the loss of the soil arch effect and the failure of the anti-slide pile effect.(3)Based on PLAXIS 3D numerical simulation,the loss mechanism of soil arch effect under the fluctuation of reservoir water level is further studied.Through the simulation analysis results,it is concluded that the law of numerical simulation soil arch effect is in accordance with the law of physical model test,both of which are due to the periodic fluctuation of reservoir water level and the landslide thrust effect,which has a more direct influence on the leading edge soil mass and the soil between anti-slide piles.Soil arch bears the sliding thrust,while the thrust applied after the fluctuation of reservoir water level leads to the increase of soil moisture content.When the sliding force increases to a certain value,the equilibrium condition of soil arch is destroyed,resulting in the loss and destruction of soil arch effect.When the soil arch effect is lost,the maximum slip of soil behind and between piles due to the loss of soil arch effect indicates that the soil arch effect is damaged and the anti-slide pile support is ineffective.