Study On Load Transfer Mechanism Of Pile-soil For Uplift Pile

As a main form of pull foundations, uplift piles have wide application in practices. Ourknowledge about tensile bearing properties of piles is relatively insufficient in contrast withthat of bearing properties of compressive piles. It is important to get the deformationcharacteristics of uplift piles under vertical loads from the studying on load transfermechanism of pile-soil.Based on the past studies, analysis is done on load transfer characteristics of uplift pilesand compressive piles combined with pile-side resistance softening, which shows that thecharacteristics are the same formally. But differences exist. They are Poisson’s ratio of pile,dilation of soil, rotation of principal stress axes of pile-side soil and so on. Influence isdemonstrated by the stress increment due to principal stress axes rotation angle increment.Distribution state of pile-side resistance is demonstrated while uplift pile catching itsbearing capacity, which is when loss of bearing capacity due to the softening of upperpile-side resistance equals the increase due to the exerting of lower pile-side resistance.Tri-linear model is set up for pile-side load transfer. Pile-side soil is divided into elastic stage,softening stage and slip stage due to the exerting level of pile-side resistance. Analyticalsolution is derived in the three combinations of the stages in the range of bearing capacity.Calculation process is described while using the analytical method to solve the single piledeformation under tension load. The physical meaning of s in the load transfer differentialequation is different from the elongation of pile. The case in publications is studied by usingthe analytical method, which shows that the calculated values are of well agreement withmeasured values.The tests of single pile under tension load in publications are simulated by using FLAC.The simulated load-displacement curve and pile-side resistance exerting curve of one of thesoil layer are compared with those got in the tests, which shows the validity of FLAC insimulating the mechanic performance of tension piles. Further, some material properties ofpiles and soils, including young’s modulus of pile, Poisson’s ratio of pile, Poisson’s ratio ofsoil, cohesion of soil, friction of soil, Pile-soil interface shear stiffness, normal stiffness,cohesion and friction, are analyzed in influencing the up-displacement of tension piles. Some valuable learning about influential discipline of the factors on the stress and deformationmechanism of tension piles is summarized.