Deformation Mechanism Of Pile Anchor Retaining Structure In Deep Foundation Pit And Its Influence On Stable Soil

The pile-anchor retaining structure is widely used in foundation pit engineering due to its advantages of good stability and small deformation,a lot of engineering practice shows that the stable soil around the anchor cable section of pile-anchor retaining structure may be damaged,this kind of damage is not checked by the current standard,so there are safety risks.The form is a crack parallel to the edge of the pit on the surface outside the foundation pit,the crack appears roughly near the end of the anchor cable,and extends downward along the end of the anchor cable and is connected.The end of the anchor cable is often beyond the red line,this kind of damage may cause disputes at the least,or lead to the failure of anchor cable,and then lead to the serious consequences of foundation pit damage.This paper takes a deep foundation pit in Handan City as the background,the failure mechanism of soil in anchor section of pile-anchor retaining structure is discussed by means of finite element software,the factors affecting the failure of stable soil are also studied.In addition,the deformation mechanism of pile-anchor supporting structure is also discussed,the influence of free section of anchor cable and prestress on the deformation of foundation pit is discussed.Related research contents include:(1)An engineering example in Handan City was analyzed,a section of foundation pit is selected for numerical simulation to analyze the surface settlement and the horizontal displacement of supporting pile after excavation,the reliability of the model is verified by comparing with the measured results and the theoretical calculation results,it is feasible for further analysis of foundation pit deformation and stability of soil.(2)By observing the PEEQ cloud map of the model,it is found that there is a risk of "soil instability in the anchorage section" failure in the foundation pit.With the help of finite element software,the influence of prestress of anchor cable,length of free section of anchor cable,length of fixed section of anchor cable and soil strength on stability failure of foundation pit is analyzed.By observing the change of plastic deformation range of anchor section soil and the change of instantaneous plastic change of foundation pit surface under different parameters,it is concluded that prestress can increase the disturbance range of stable soil.Due to the improper value of soil-anchor cable friction coefficient and insufficient soil-anchor cable friction resistance,prestress will increase the risk of damage of stable soil;The free section and anchor section can improve the deformation of the foundation pit stabilized soil,and the damage effect of the foundation pit stabilized soil gradually disappears;Soil layer high strength of the foundation pit,soil stability damage range is smaller.(3)The free section of anchor cable can reduce the horizontal displacement and surface settlement of foundation pit retaining pile.Based on the length of free section in the design of this project,increasing the length of free section of anchor cable will decrease the displacement of supporting pile and the surface settlement.Reducing the length of free section of anchor cable will increase the displacement of supporting pile top and the maximum surface settlement.(4)The prestress of anchor cable can effectively improve the internal force and displacement of retaining pile and reduce the horizontal displacement and surface settlement of retaining pile.When the prestress is not applied enough,the horizontal displacement of supporting pile top increases obviously,and the closer the ground settlement is to the foundation pit,the faster the foundation pit settlement increases.