The Finite Element Analysis In Deep Excavation Of Loess Region

From the 1980s till now, our country has made great progress in the foundation of pit technology. However, many cities in the country foundation pit projects happened also many works accident due tolack of experience and the possession of immature technology.This paper presents a design of deep foundation pit, using Plaxis finite element software to simulate the impact of foundation pit comprehensive analysis of the design factors. It studied foundation pit of a high-rise residential building in Xi'an, the main research contents as follows:First, I analyze working mechanism of pile-anchor retaining structure;Second,I study the theory of pile-anchor retaining structure theory,and descripe the adwantage and disadvantage of the various throries.Third, I study the the basic principles of finite element numerical simulation,and gives a brief description of Plaxis.I used it to simulate the excavation and the supporting progress, The results as follows:From the results of the analysis,the greater of the bolt prestress is,the smaller of the pile top displacement is, but it should increase correspondingly to increase the flexural capacity of pile cross-section. With the anchor down locations, the displacement of pile head increased, the maximum bending moment of pile reduced, so in the project, if the deformation meet the specifications, righting down the anchor position is favorable to the strength of pile, so we can reduced the pile diameter to reduce the project cost.If increase the supporting structure stiffness, the moment the value of supporting piles will also be gradually increased,and it is adverse to the strength bearing pile, From the economic point of view, increasing the pile diameter is bound to increase the project cost. Supporting structure of the insertion depth should meet certain requirements, If the depth of shallow buried, will lead to kick damage. Increasing insertion depth can effectively reduce the displacement of piles, When the insertion depth meets the requirements of the stability of supporting structure, continue to increase into the depth of the control of the deformation effects are not obvious. With the groundwater declining, ground subsidence increases and pit bottom of heave decreases, These two aspects should be integrated and rainfall reasonable.