Analysis Of Factors On Effect Of Horizontal Displacement And Internal Force For Secant Pileof Deep Foundation Pit

The supply of large city urban space is becoming more and more tense,in order to meet the requirements of urban construction,large-scale development of urban underground space is particularly urgent.This is bound to bring a lot of deep foundation pit works,because the deep foundation pit works in the city center where there are lots of buildings and full of underground pipes.This requires that the retaining structure the deep foundation pit must be stable and reliable and meet the surrounding environment of the deformation control conditions.Therefore,the analysis of internal force and horizontal displacement in the design of deep foundation pit retaining structuret is very important.This paper takes the deep foundation pit project of Gaopu Road in Xiamen as the research background.Using the equivalent beam method,incremental method,numerical simulation method,field deformation monitoring analysis distribution law of internal force and horizontal displacement of secant pile and inner support structure in deep foundation pit.At the same time,the effects of pile diameter,embedded depth of supporting piles,secant degree of secant pile,supporting preloading axial force,supporting erection position,supporting stiffness and other factors on the horizontal displacement of supporting structure are analyzed.The main results of this paper are as follows:(1)The law of the bending moment obtained by the incremental method and the numerical simulation method is very similar.It is reasonable to use the incremental method and the numerical simulation method to calculate the bending moment of pile.And for the three support above the foundation,the calculation results of pile bending moment of equivalent beam method is significantly larger than others.(2)The horizontal displacement curve that obtained by incremental method,numerical simulation method and actual monitoring method are very similar,the maximum horizontal displacement position of the pile that obtained by these three methods is relatively close.It is shown that incremental method and numerical simulation method are correct for calculating the horizontal displacement of supporting structure.The difference between the maximum horizontal displacement obtained by incremental method and numerical simulation method is very small,while the actual monitoring maximum horizontal displacement is greater than the numerical simulation method and incremental method.(3)When the pile diameter is small,the increase of pile diameter can significantly reduce the maximum horizontal displacement of pile,but when the support pile diameter increases more than a certain range,the effect of the maximum horizontal displacement of the support pile gradually weakened.The increase of the embedded depth of the support pile can reduce the whole horizontal displacement of the pile,and the decrease of the embedded depth will cause a significant increase in the horizontal displacement of the pile bottom.(4)With the increase of secant degree between the pile,the maximum horizontal displacement of the pile is obviously reduced,but the change of horizontal displacement of the pile top and the horizontal displacement of the pile bottom are small,and the extent of reduction of maximum horizontal displacement of the support pile is gradually reduced.(5)When the steel support pre-axial,and with the increase of the pre-applied axial force can significantly reduce the pile top and the maximum horizontal displacement.And the displacement of the support pile below the bottom of the excavation hardly changes.But when the pre-axial force is too large,will increase the bending moment of the pile,so it is not advisable to increase the pre-axial force of steel support to control the deformation of the support pile.(6)Increasing support stiffness will significantly reduce the maximum displacement of the pile and has little effect on the displacement of other parts.But when the support stiffness reaches a certain range,continue to increase the support stiffness to control the displacement of the pile is not obvious.