Analysis And Reserch Of The Mechanical Characteristics Of The Steel Pipe Piles Under Pressure-Bending-Shear Load Based On Prototype Pile Foundation

The super-long and large diameter steel pipe piles are widely used in bridge pile foundation, because of the high bearing capacity, good flexural capacity, simple process and small soil disturbance. The steel pipe pile is composed of steel tube and core concrete filling in it. Its basic principle is the confinement effect on the core concrete made by steel tube, so that the core concrete is in the three state compression. The core concrete has high compressive strength and compressive deformation ability, and the steel tube has high carrying capacity, so that the combination of them has strong stiffness. However, research on the large diameter steel pipe pile is still very insufficient, especially the research of steel pipe pile in the pressure-bending-shear loads considering the influence of pile cap, the pile group effect and soil factors.In view of this situation, this paper relies on the Hong Kong-Zhuhai-Macao Bridge Pile Foundation Engineering, combined with the model test of part foundation, the numerical simulation of prototype pile and calculation analysis to make comparison and analysis of prototype pile’s mechanical characteristics in the pressure-bending-shear loads, and obtained the following conclusions:(1) the vertical deformation increased linearly with the axial force; horizontal displacement increased linearly with the shearing force and moment, and the maximum horizontal displacement is in the top of the pile, the minimum one is in the bottom of pile; the vertical and horizontal deformation of this six steel pipe piles in the foundation are consistent, but the stress of the middle piles are about1.3times than the corner piles;(2) The compressive strain in axis one increases at the upper and reduce at the bottom with the increase of work load, the compressive strain in axis three is in contrast with axis one, the compressive strain in axis two slightly decreased with the increase of work load; on the whole strain of the middle piles are9%greater than the corner piles;(3) The compressive strain of steel tubes are greater than the core concrete, it doesn’t accord with flat section deformation assumption;(4) The stress ratio of the steel tube and the core concrete is about6, so that the vertical load ratio of the steel tube and the core concrete is about1:3;(5) Because the prototype pile foundation is end bearing pile foundation, so that the pile side friction of the middle piles and the corner piles are basically the same; the resistance in the bottom of the middle piles are greater than the corner piles, and the resistance in the first row is greater than the second;(6) The vertical deformation、horizontal deformation and longitudinal strain of the part pile foundation model test and the prototype pile foundation in the numerical simulation are consistent in the pressure-bending-shear loads. But the deformation and strain in the prototype pile foundation are less and more stable than the one in the part pile foundation.