Model Tests And Numerical Analysis Of Pile-Soil-Platform Nonlinear Interaction

These days, pile-raft foundation have widely applied in civil engineering, we have achieved great harvest of study in it, but now its design theory and design method which thinking over pile-soil-raft interaction still mostly based on elasticity analysis, and its analysis result not accord with fact. To solve these problems, we must introduce nonlinear work character, which was accord with practice work state of foundation and piles foundation in analysis. Based on understand limit of pile-soil-pile caps nonlinear interaction and locate test at present, the task we studied on pile-soil-pile caps nonlinear interaction work character by means of model test and numerical simulation, and find a lot of beneficial conclusion. Main parts of this paper are as follows: 1. By design model test of pile-soil-pile caps interaction, we studied on nonlinear work character of pile caps, single pile and a pile with pile caps which by the action of load. P-S curve was acquired in nonlinear work condition, also we achieved the distribution law of pile side friction, pile end resistance and counter force under pile caps and so on. Based on these results, we carried through pile group with pile caps model test for general and big pile space. By comparison analysis of model test, we summarized the pile-soil mechanism of action by pressure and their nonlinear interaction law when changed with load, which enhanced our understanding of pile-soil-pile caps nonlinear interaction mechanism. Test result show that when the group pile destroyed, its mean counter force under foundation is more than mean counter force under foundation of a pile with pile caps. This fact provided test proof for theory analysis of soil ultimate bear capacity heightened in the case of barrier effect of pile. 2. Using 3D Finite Element Method (FEM), we carried through numerical simulation to model test. Based on reasonably calculate parameter by back analysis of model test results, we carried through more simulate analysis to correlation model test. The calculation result show that the result of numerical analysis and the result of test have well consistency, which indicate that when reasonably accept the soil constitutive model and calculate parameter, 3D FEM can used to analysis of the pile-soil-pile caps interaction efficiency. Soil deformation and vertical stress distribution law between piles, which gained from numerical simulation for big pile space, verified the hypothesis that soil deformation need consider the deformation of soil between piles in settlement calculation of composite pile foundation. Soil displacement field distribution law under pile caps revealed the fact that the soil flow around the pile by barrier effect of pile, show that the soil under pile caps have exist the probability of conquer the resistance of flow around the pile wall and occur lateral extrusion destroy. This will have positive guidance meaning to study the destroy of composite pile foundation. 3. With the literature information in existence, we not see the similitude correlation report, which use model test and combined 3D numerical simulation carry through comprehensive study to pile-soil-pile caps interaction. The achievement that soil ultimate bear capacity heightened under pile caps due to barrier effect of piles gained from model test, and soil move around piles acquired from numerical simulation, its not only verified hypothesis of composite pile foundation nonlinear design theory, but have important reference value to the study of design theory and design method of composite pile foundation, which help to go deep into study of promote pile-soil-pile caps nonlinear interaction theory and composite pile foundation nonlinear design theory.