A Preliminary Study On Raft-Composite Foundation Of CFG Pile Interaction

Nowadays, Pile foundation has been used in high-rise or super high-rise buildings by civil engineers, using of pile has a good result, but the bearing capacity of soil between piles has not been fully exploited, especially, the bearing capacity of soil between piles is higher, the waste is more. If the composite foundation is taken, the pile and soil bearing capacity will play sufficiently and reduce the pile layout, CFG pile is one of these piles. CFG pile has high strength, stiffness, low-cost, short construction period etc, which can improve the bearing capacity as well as control the ground deformation. At present, the CFG pile has been used associate with raft foundation and box foundation in practical project such as high-rise buildings, and achieved good economic and social benefits, which has become a top research by geotechnical workers. The main previous studies focus on traits of single-pile or multiple-pile, the research of this paper will be on the raft foundation-CFG pile system by vertical loads.Firstly, the research status and theoretical result of CFG pile multi-foundation, and the content of this paper is put forward. Secondly, the basic theory which the raft foundation-CFG pile joint together is expound,the overall equation of CFG pile under common role is established. Then, large-scale finite element software ANSYS, as well as the simulation process used by SOLID45 element and the material constitutive model is introduced in this paper. Finally, with ANSYS finite element analysis,considering the raft foundation-CFG pile work together, analyzing the influence of CFG composite pile foundation traits. In the light of actual project, the settlement of construction is simulated.Some results are obtained base on analyzing raft foundation-composite foundation of CFG pile interaction.1) The change of the raft thickness is inversely proportional to the foundation settlement and stress of pile top, it has direct ratio relations with stress of soil among pile and pile tip soil.2) The change of the cushion thickness had no significant influence on the foundation settlement and stress of pile tip soil, but it has an important effect on pile-soil stress distribution. Thickness increase of cushion can reduce stress of pile top, the bearing capacity of soil among pile will play sufficiently. The reasonable cushion thickness is obtained with simulation, which is 0.2-0.3 meter.3) The ratio of pile-soil modulus has direct ratio relations with foundation settlement and stress of pile top, but it is inversely proportional to the stress of soil among pile and pile tip soil.4) The replacement ratio is inversely proportional to the foundation settlement and pile-soil stress. The replacement ratio can be adjusted by pile spacing, the general condition of pile spacing is quadruple with pile diameter.