A Study On Bearing Behavior Of Large Diameter Pile Under Vertical Load

Along with the economic rapid development of our country, the appearance of moderate-high or high buildings and large-span bridges make the use of large diameter pile foundation which has the advantage of high bearing capacity popular. But the load transfer mechanism of this type of pile is not distinct. By now, there is no method which agree with practical situation. The design method of large diameter pile in the applicable codes and standards cannot reflect the mechanism of load-bearing and deformation. Therefore, the study on the load-bearing properties of the large diameter pile is important to meet the requirements of the theory and the reality.At first, the methods, which have been used to decide the bearing capacity of large diameter pile, and their respective advantages and disadvantages are summarized, and the bearing behavior of large diameter pile and load transfer mechanism of single pile are discussed in this paper.In the next place, for the three dimension finite element calculation of the single large diameter pile under the vertical load, it can be simplified to the axisymmetric problems. The quarter of the pile has been chosen to analyze. The elastic constitutive model and the elasto-plastic constitutive models have been adopted to simulate the pile and soils respectively. And it has been adopted the master-slave contact surface model when simulating the contact behavior between the pile and soils.Thereinto, to assure the shape of the extended Drucker-Prager yield surface convex, when it approached to the Mohr-Coulomb yield surface, the friction angle of soils is less than or equal to 22 degree, if the extended constitutive model has been adopted as the soil model. If the friction angle of soils is more than 22 degree, it can adopt the Mohr-Coulomb model as the soil model. The analysis of these examples demonstrate that the method has been proved to be effective when determining the capacity of large diameter pile.Thirdly, the large diameter pile load-bearing properties in isotropic soils, layered soil and rock are simulated by the axisymmetric finite element method. The load-settlement relationship curve, the exertion of the lateral friction resistance, the transfer of the axial force and the change of the displacement of pile are analyzed in this three situations. Meanwhile, it has discussed the factors which can influence the relation of settlement and force, including pile-length, pile-diameter, rocked depth, the...