The Analysis Of Retaining Structures Of Deep Excavation Under The Bridge Of Underpasses

With the development of the city capital construction, deep excavation pits not only increase, but also develop further. Large quantities of deep excavation pits engineering concentrate in the downtown, so the construction engineering has the special character as below: The first is construction field would be narrow and small. The second is construction has complicity condition and the third is construction engineering affects the roads and different kinds of municipal buildings nearby, etc. How to decrease the effects has become very important for people's consideration. The paper deals with the optimization design of cantilever row piles retaining structure. The main aspect is as follow:(1) If the mechanic property of soil is bad, it's better to use secant pile wall. The research on the theory and the design method of the secant pile wall composite Structure used as permanent structure is studied in the paper. At the same time, the paper discusses the feasibility of different secant pile wall used as permanent structure and includes that the hard /hard secant pile wall can be used as permanent structure and hard / firm as a part of permanent structure, the joints between secant pile wall and the exterior wall of the major structure are also presented.(2) As for clay soil, it is reasonable to use solider piles because of the existence of soil arching effect. The finite element analysis software package, ANSYS, is used to study soil arching effect of anti-slide pile, and the effects of factors on the behavior of soil arching effect such as pile spacing, properties of soil, interface of soil-pile and the movement of pile are discussed in detail in this paper.(3)Combined with the analysis of anti-sliding pile , analyzed the interaction of anti-sliding pile with the surrounding soil by three-dimensional numerical modeling, analyzed the characters of anti-sliding pile and surrounding soil, the deformation trend of anti-sliding pile and surrounding soil and stress trend . The results showed that: the main influence factors are the sustentation effect of anti-sliding pile and the earth-arch effect. High cohesion soil will increase anti-sliding piles'reinforcement. The increase of pile spacing will increase the largest displacement and the relative displacement between the pile and earth, arise excess soil that between piles being extruded and make the anti-sliding pile invalid when the extent exceeds the requirement.(4) Developed the Duncan-chang constitutive model in ANSYS software by means of the secondary developing technology of ANSYS. Using different soil constitutive models including the Duncan-chang constitutive model, Druker-Prager elastoplastic model, the paper analyzed the interaction of anti-sliding pile with the surrounding soil in clay soil by numerical modeling in order to obtain the influence of different soil constitutive models to the earth-arch effect between piles.This paper is just a preliminary study on how to choose the suitable supporting structure of pit, to develop a perfect design method, there is still a lot of further work to do. The results of research and relational conclusion will perfect the analysis theory of the pit support structure, and provide references for the designs of similar engineering projects.