Force Analysis And Numerical Simulation Of Pile-anchor Retaining Structure Of Deep Foundation Pit

With the advancement of urbanization construction pace of our country，high-riseand super high-rise buildings are concentrated in the central tertian of cities. Overalltrends of foundation pit engineering show the characteristics of large，thick，deep and soon. In order to make the deep foundation pit engineering satisfy the requirements ofsafety， economy， environmental protection and sustainable development， deepfoundation pit engineering should satisfy not only the demands of itself deformation andstability but also the standards of surroundings of foundation pit deformation control inthe process of excavation.Compared with other retaining structures， pile-anchor retaining structure hasadvantages in such as larger space of construction，wider scope of application，lighterpollution of environment，which has widely used in deep foundation pit engineering ofindustrial buildings and landslide treatments etc，so the researches of its design theoryand application are more active. Due to complex deformation mechanism and manyinfluencing factors are taken into consideration，there is not a uniform of calculatingmethods until now. So it is of great significance of theory and practical value ofengineering to develop the research of deformation and force analysis of pile-anchorretaining structure.The excavation of foundation pit belongs to unloading behavior of earth，which isa complex mechanical process，with the interaction between retaining structures andearth，and continual adjustments of itself deformation and force，as a result， the earthwill reach a state of stability or instability. The dip angle of anchor，embedded depth ofpile and the earth pressure on the retaining structure etc all affect the lateraldisplacements of side wall in the design of retaining structure of foundation pit，especially the distribution and precision of numerical value of earth pressure are vital tothe optimal design of retaining structure. Based on the research achievements ofpredecessors，equivalent beam method and elastic foundation method are jointly used inthis paper to design and calculate the pile-anchor retaining structure of deep foundationpit engineering of Tangshan，with comparisons of results based on joint design andnumerical analysis，achieving the following main conclusions： (1) Even though the equivalent beam method can well solve the problem ofembedded depth of retaining pile，compared with finite difference method，the results areold-fashioned，which have optimal space to promote to reduce the cost of engineering.(2) Although elastic foundation beam method can predict the horizontaldisplacement and internal force of retaining structure，with the inadequacy of theory，cannot take the interaction of pile-anchor-earth into consideration，cannot reflect thethree-dimensional space effect on the process of excavation，all lead to old-fashionedresults when compared with numerical analysis of finite difference method；In terms ofanalysis and application of horizontal displacement of retaining structure， finitedifference method can basically meet the standards of deformation control and reflect thethree-dimensional space effect on the process of excavation.(3) The calculating results of finite difference method show that the maximum valueof horizontal displacement and positive moment of pile appear in0.85H (H stands for thedepth of excavation) and the negative moment appears in1.3H after the excavation; themaximum value of active and passive earth pressure appear in1.3H rather than thebottom in the range of pile length; the requirements of deformation control and overallstability of foundation pit can be satisfied with0.5H which as the embedded depth of thepile，and the dip angle of anchor is appropriate when it ranges from5°to25°but less than30°.