| Along with the vigorous development of China's economy, a large number of constructions were constructed. Therefore, it becomes very important for our country to save the limited resources in various types of constructions. Composite pile foundation has been the hotspot to geotechnical research workers for its good economic efficiency and broad application prospects, because it can significantly reduce the number of piles. This subject has been researched by experts and scholars at home and abroad for decades, but a perfect design theory and calculation method has not been formed. So, the reciprocity of composite pile foundation and soil and support platform should be studied and discussed further.Theory of composite pile foundation means that the piles, soil and support platform support the load together, industry and civil construction foundation uses this theory a lot while bridge foundation uses it little. The active《criterion for groundsill of road and bridge and basis designing》just regulate three kind of basis: extend foundation, pile foundation and well-sinking foundation. When the vertical carrying capacity be calculated, only the pile tip resistance and lateral resistance taken into account, while the support capacity of soil under the platform of pile foundation was ignored. Compare with the section area of pile, the platform of pile foundation is great, so it can bring obvious benefits to take the support capacity of soil under the pile foundation into account.The main work is as follows:①Brief review on the development of Composite pile foundation theory and its application in bridge.②This paper introduces the destroy pattern of composite pile foundation and how to transfer and support the load, and analyses the mechanism and correlation of support platform–pile-soil; introduces the concept of yield surface and destroy surface in theory of elasticity-plasticity model, and moreover introduces the Mohr-Coulomb yield criterion, Drucker-Prager yield criterion and the Cambridge criteria,And the models on their basis.③This paper introduces the finite element method which is widely used in engineering analysis briefly, including development and basic process of finite element method, and eight nodes hexahedron common use in finite element method analyze. Then briefly introduces the ABAQUS6.4 program broad use in rock and soil engineering domain, including the main analysis module, graphical interface processor CAE modeling the process of introduction and.④This paper establish 3D none linearity finite element model by ABAQUS program to analyze the infection of settlement in centre of platform, percent of load for pile and soil, addition stress in soil when the thickness of platform is different, elastic modulus of pile is different, soil deformation modulus is different, thickness between soil and pile is different, space between pile is different, Drawing the corresponding rule to provide guidance for the actual engineering design of composite pile foundation, to make the design accord with the actual situation more.⑤In this paper, experiment on ChenPing bridge in freeway from XinMin to TieLing is carried, the result was analyzed contrast to the result received from the model established by ABAQUS program.Through the study on model established by ABAQUS program and engineering example, a few conclusion gained:1,Infection to overall sedimentation in the center of platform:①along with the accretion of thickness of platform, elastic modulus of pile, deformation modulus of soil between the pile and soil on the top of pile, the overall sedimentation in the center of platform minish;②along with the accretion of space between piles, the compress capacity of soil between the piles rise while the compress capacity of soil under the top of pile hold the line, which make the overall sedimentation in the center of platform rise subsequently.2,infection to load percent of pile and soil:①along with the rise of thickness of platform and elastic modulus of pile, the load percent held by pile rises;②the load percent held by pile reduces along with the accretion of deformation modulus of soil, and the trend of reduce become slow;③the load percent held by the pile rises along with the accretion of the thickness of soil between piles and the space between the piles, and this trend become slow.3,Infection to the additional stress of soil:①Along with the thickness increase of support platform, the additional stress in the soil from the top of pile to a certain depth decreased;②Along with the increase of elastic modulus of the pile, the additional stress between pile and soil decrease, and it remain unchanged under a certain depth;③Along with the increase of deformation modulus of soil between piles, the additional stress of soil between piles from the top of piles to a certain depth increase; Along with the increase of deformation modulus of soil at the top of piles, the additional stress of soil between piles changes little, while the additional stress of soil at the top of piles increases, and the rate becomes slow;④Along with the depth of soil between piles increases, infection to additional stress increases, the deeper, the smaller;⑤Along with the space of piles increases, additional stress of soil between piles increases. When the space is big enough, the additional stress of soil at the top of piles changes little.4,By analyzing the working properties of foundation in different parameter, drew corresponding disciplinarian, to provide help for designing bridge foundation, making the design accord with practice.5,The sedimentation on the first platform in ChenPing bridge is close to the result calculated by the finite element model, testify the veracity and reliability the 3D finite element model established by ABAQUS, and the sedimentation capacity satisfy the criterion.6,The analysis on engineering of ChenPing bridge indicates that The carrying capacity of soil is still has much room to develop, so the amount of piles can be reduce properly to save cost.
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