Study On Bearing Characteristics Of Pile Based On Load Transfer Method

Pile foundations have been studied for a long time because of its wide application to various structures. However, how to accurately calculate the bearing capacity and displacement of piles foundations is still a great problem on account of the variation of soil type, construction method, loading conditions and etc. The shaft resistance and the toe resistance are two key factors in this calculation. The shaft resistance has significant nonlinear property while the presence of toe debris has inevitable effects on bearing capacity. Moreover, piles applied in bridges, high-rise buildings and port engineering are often subjected to inclined loads. The stocking on ground near the pile may cause displacement of soil, which is a main reason of negative friction.This thesis mainly focus on bearing capacity of piles under axial and inclined loads based on summary of previous research on piles under different kinds of loads. The failure mode of pile under axial load is analyzed and the p-s curves under different modulus of the toe soil and friction angle are calculated. A hyperbola model is used in the thesis to describe the shaft resistance of pile with consideration of the nonlinear behavior of load transfer along the pile length. Meanwhile, in order to take account of the influence of toe debris during the pile construction, a trilinear model is used to represent the resistance at pile tip. With considering the nonlinear characteristic of load transfer, the layered stratum and the pile-soil interaction, the differential equation for the pile is established. Its relative solution is obtained by programming with VB using power series method, and the influence of hyperbola model and toe debris are analyzed. A pile test data was compared with the current solution. Results indicate that the hyperbola model fits the field data well, and the calculated p-s curve agrees well with the measured one. Then, the bearing behavior is discussed in this thesis and the comparison of different computing methods is made. For the pile under inclined load and ground stocking, field tests under horizontal load and ground stocking are simulated using finite element method. Good agreement is obtained, indicating that the finite model can simulate its behavior accurately. Furthermore, the bearing capacity and displacement of piles subjected to inclined load and ground stocking are investigated. In the analysis process, the axial load is applied firstly, then the horizontal load and ground stocking load are applied to the order. The bearing behaviors under different ways and different magnitude of loads are studied, the influences of load order and load magnitude are analyzed. Based on the obtained results, a series of qualitative conclusions are drawn which can be applied to guide engineering practice.