Study On Bearing Behavior Of Rigid And Flexible Pile Composite Foundation In Coastal Soft Soil

With the continuous development of China's economy,the land utilization rate in coastal areas is getting higher and higher.In order to improve the bearing capacity of soft soil in coastal area,the technology of rigid-flexible pile composite foundation came into being.Compared with the rigid pile composite foundation commonly used in the coastal area,the rigid-flexible pile composite foundation has the advantages of accelerating the consolidation of soft soil drainage and reducing the engineering cost,which is gradually used in more and more engineering projects.This paper takes an apartment building project in the coastal area as the engineering background.Finite element software ABAQUS and field load test were used to study the bearing behavior of rigid-flexible pile composite foundation under soft soil of coastal phase.The research contents of this paper mainly include the following aspects:(1)the engineering examples and development of rigid-flexible pile composite foundation under coastal soft soil are introduced,and the research status of rigid-flexible pile composite foundation at home and abroad is summarized.This will provide an idea for the future research direction of rigid-flexible pile composite foundation under coastal soft soil.(2)the basic principles and methods in the design process of the composite foundation of rigid and flexible piles are summarized,including the settlement calculation formula of the composite foundation of rigid and flexible piles,the calculation formula of the bearing capacity of rigid piles,the calculation formula of the bearing capacity of flexible piles,etc.It is found that the bearing capacity formula of rigid-flexible pile composite foundation under coastal soft soil does not fully consider the effect of drainage consolidation of flexible pile under the existing standard conditions.Based on the analysis of the working principle of rigid-flexible pile composite foundation,a modified formula for calculating the bearing capacity of rigid-flexible pile composite foundation under binhai soft soil is proposed.(3)according to the design parameters and soil layer information of the project on which the paper is based,the model of rigid-flexible pile composite foundation is established and calculated by using ABAQUS,a large general finite element calculation and analysis software.Research play coefficient of rigid pile and flexible pile coefficient and the relationship between the coefficient of soil between piles play,summarizes the change of the coefficient of friction of piles and soil under the just-the general rule of flexible pile composite foundation load-bearing properties,the results show that the coefficient of friction of piles and soil between 0.10 ~ 0.15,the coefficient of composite foundation bearing capacity to play the most stable,each component to maximizing its bearing capacity.The value range of the play coefficient of rigid pile is 0.89~0.98,the value range of the play coefficient of flexible pile is 0.66~0.83,and the value range of the play coefficient of soil between piles is 0.63~0.84.(4)the method for determining the bearing capacity performance coefficient of rigid-flexible pile composite foundation is studied,and the numerical simulation results are compared with the in-situ experimental data of engineering examples to verify the results of chapter 3 numerical simulation and the range of bearing capacity performance coefficient of rigid-flexible pile composite foundation.