Research On Uplift Pile Bearing Mechansim Of The Integrated Structure Of Subway Station And Overpass

The urbanization accelerates in recent years and more and more people is pouring into develpoed cities which makes lots of traffic jams. A variety of high-rise buildings springing up and more underground space has been develpoed. Pile foundation is widely used in this structures with good mechanical performance.According to the force form, pile foundation is divided into uplift pile and bearing pile.The study for bearing pile is mature at home and abroad while uplift pile is opposite.Studies on uplift piles are mostly concentrated on the study of bearing capacity which based on model tests or experience mostly. Theoretical study on bearing mechanism,pile deformation, pile ground foundation is rarely. In this paper, the mechanism of pile foundation bearing systematic studied, research focused on the uplift pile bearing mechanism, combined with vertical and horizontal load test data. Hefei Mingguang Road subway station as a study case. The main contents of the following:?The load transfer mechanism between uplift pile and bearing pile is different.At present, the academic community generally considered to the damage forms of uplift pile are similarity to friction piles. In initial stage, the anti-pulling force is mainly provided by the upper earth, the friction resistance of the upper part of the pile is always releases first. With the increasing displacement of the pile, the friction resistance can not resist and stress dispersion downward until pile destruction. Pile destruction forms depending on the number of piles and spacing.?There are three kinds of failure modes with uplift pile: the inverted frustum shear failure, alone interface shear failure and complex shear failure. Introduce seven most common load transfer functions. Example with Tomlinson method, Patra method,theoretical analysis method and regression formula method were calculated and compared with the actual data, the regression formula method is the most convenient and accord with reality. Factors affecting the bearing capacity of group piles,introducing pile group efficiency factor to reflect the effect level.?Applied to the horizontal force or bending moment, the pile deflection which perpendicular to the axial direction may occur. With the force or moment increases,soil cracking and ridges appeals, horizontal displacement of the pile will increase gradually also, When the horizontal displacement of the pile deformation exceeds the limits, the pile will damage with pile cracks, fracture, even pull out. In the mechanicalcharacteristics of the pile, which can afford vertical bearing capacity is much greater than the level of capacity, and therefore the size of the horizontal bearing capacity of the pile design often becomes a limiting condition. The main factors affecting the horizontal bearing capacity include buried depth, displacement limit, section stiffness and so on.?Pile settlement research. Represent by settlement, differential settlement, the overall tilt, partially inclined.?Research on pile settlement and axial force by simulating Hefei Mingguang Road subway station use Midas GTS NX. The settlement which is mainly minus displacement of the uplift pile increases with the depth of excavation and the maximum appeared in the last step of the excavation.