Numerical Simulation And Analysis Of Pile-anchor Support Structures For A Deep Foundation Pit

With the continuous development of social economy,urban land use is becoming more and more serious,and a large number of urban underground projects have been built,which makes the foundation pit project continue to develop in a larger and deeper direction.The deformation of supporting structure in the construction process is closely related to the engineering quality of deep foundation pit.It is necessary to select the supporting method from the aspects of safety,reliability and economic applicability.Pile-anchor support is more adaptable than other supporting methods,which can effectively restrain the sliding failure of soil,limit the displacement of foundation pit soil,and save engineering cost.It is a very common supporting method for deep foundation pit.There are many factors affecting the deformation of pile-anchor retaining structure,but there are still some gaps in the study of the factors affecting the deformation of pile-anchor retaining structure.Based on the background of Jinlong Fortune Deep Foundation Pit Project in Mengzi,this paper uses finite element software MIDAS/GTS to build a three-dimensional model to simulate the dynamic construction process.The main contents are as follows:(1)Through consulting relevant literature and information,the characteristics and application scope of foundation pit support mode,interaction mechanism and destructive characteristics of Pile-anchor support are summarized,and the analysis theory of support structure is summarized,which provides theoretical basis for subsequent research.(2)This paper introduces the site geology and surrounding environmental conditions,briefly introduces the support scheme,and establishes a three-dimensional finite element model using MIDAS/GTS.(3)Based on the engineering design,the finite element model is established,and the distribution condition is established according to the specific construction procedure.The variation law of internal force and displacement of the support system in the dynamic construction process is analyzed.The simulation results show that the maximum horizontal displacement of supporting piles occurs at the top of piles,which is 33.01mm.The maximum negative shear force of supporting piles occurs in the middle and lower parts of piles.The maximum negative bending moment of supporting piles occurs in the middle and upper parts of piles.The maximum positive bending moment occurs in the middle and lower parts of piles.The settlement of soil around the foundation pit reaches the maximum settlement of 8.72mm 7 m away from the edge of the foundation pit.By comparing the simulated value with the monitored value,it is found that there is little difference between the simulated value and the monitored value,which verifies the feasibility and validity of the finite element method and provides an effective numerical model for the follow-up study.(4)The influence of pile diameter,pile spacing and pile length on the horizontal displacement and bending moment of supporting pile is analyzed.When pile diameter or pile length increases or decreases,the horizontal displacement of supporting pile can be effectively restrained,but there is an effective value of pile diameter and pile spacing.When the effective value is exceeded,the influence on the deformation of supporting pile is not obvious.The change of pile diameter and pile spacing will change the bending moment of supporting pile,but the effect is not obvious.By comparing the construction cost,it is found that the method of reducing pile diameter can take into account both the stability of foundation pit and the reduction of construction cost.The vertical distance between anchor cables should be between 2 and 2.5 m.Figure[39]table[12]reference[73]...