Deformation Law And Structural Parameter Optimization Of Pile-Anchor Supporting Foundation Pit

A foundation pit is a construction space created for the underground engineering of buildings.Foundation pit engineering should not only ensure construction safety,but also control the environmental impact of foundation pit construction on surrounding buildings.Foundation pit engineering located in urban buildings is particularly important for environmental protection.In this case,not only the stability of the foundation pit,but also the influence of foundation pit deformation on surrounding buildings should be considered in the design of foundation pit support.It can be said that the design of foundation pits in cities has changed from “stability control” to “deformation control”.Based on a 17-meter-deep foundation pit project in Shijiazhuang City,which adopts slope protection Pile-anchor support structure,FLAC3 D software is used for numerical analysis.Combined with the actual monitoring data,the deformation laws of ground surface settlement behind piles,horizontal displacement of the pile top,and horizontal displacement of the pile body are analyzed.Through numerical simulation,the influence law,action principle,and applicable conditions of supporting structure parameters on foundation pit deformation are analyzed.In view of the phenomenon of excessive support in the foundation pit,the optimization design is carried out by adjusting the pile spacing and the length and angle of the anchor cable.The main work and achievements are as follows :(1)Through the comparative analysis of numerical simulation and monitoring data,it is concluded that the numerical simulation results are consistent with the monitoring data,whether it is the deformation value of the foundation pit or the shape of the deformation curve,after selecting reasonable soil layer and support structure parameters.The ground surface settlement behind the pile,the horizontal displacement of the pile top and the horizontal displacement of the pile body all increase with the excavation depth of the foundation pit.The ground surface settlement curve behind the pile is in the form of a“groove”,the horizontal displacement curve of the pile top is in the form of a “quadratic parabola” with the opening towards the outside of the foundation pit,and the horizontal displacement curve of the pile body is in the form of a “convex”,which conforms to the general law of foundation pit deformation for slope protection Pile-anchor supporting structure.(2)The influence of pile spacing,anchor length and anchor angle on the deformation of the foundation pit is analyzed.Changing the pile spacing and anchor length,and angle,change the stress state of the supporting structure,resulting in changes in the displacement of the supporting structure.Changing the angle of the anchor is one way to limit the foundation pit from deforming.It works best when the anchor is at the point where two layers of soil meet,the soil thickness is the same,and the strength of the upper and lower layers of soil is very different..(3)It can be seen from the monitoring data that the maximum value and change rate of the ground surface settlement behind the pile,the horizontal displacement of the pile top,and the horizontal displacement of the pile body are far less than the deformation control value,indicating the existence of conservative design and excessive support.By changing the pile spacing and anchor length,angle optimization design,can make the deformation value of the foundation pit close to the control value,so as to avoid excessive support,and reduce construction costs.However,because the numerical simulation fails to take into account various uncertainties in the construction,a certain amount of deformation reserve is still needed for the optimal design of a foundation pit based on deformation control.