Study The Load-transfer Mechanism Of A Super-long Single Pile And The Interaction Of Pile-raft Foundation

In the paper, the load-transfer mechanism of a super-long pile, effective length of foundation pile, the interactions of pile-raft foundation and the geotechnical centrifuge model experiment of pile foundation have studied.An exponential function is proposed as a load transfer function to analyze the load transfer mechanism of a super-long single pile. The parameters are studied how to reasonably determine. The exponential function is revised in order to overcome the demerit because the method of load transfer neglects the continuity of soil.Based on back analysis of results of a statically loading test of a single pile with optimization, geotechnical parameters of the load transfer function of layered soil around the pile and under the pile bottom are confirmed rationally. A good agreement between calculational results and testing results of several engineering cases proves that it is appropriate using the revised exponential function to analyze the performance of the super-long single pile.The finite element method is carried out to analyze the load-transfer mechanism of a super-long pile. A constitutive model of interface is put forward and used as a means of studying pile-soil interaction with Goodman interface element. A elastically nonlinear constitutive model of concrete is employed to analyze stress-strain relationship of reinforced concrete under the axial load because of enough stress of reinforced concrete of the super-long pile. A compiled finite program can solve layered soils and different characters of pile-soil interaction along the pile body caused by layered soils. According to the character of variational section of a case pile, it is considered as uniform section of pile with reasonable computing method assuring compute precision in the finite element program. Calculational results of the engineering case agree to statically loading testing results of the pile.The load-transfer mechanism of the pile and distributed mode of laterally limited fricative resistance along the pile are analyzed. Pile length - distributed mode of laterally limited fricative resistance and axial stiffness of a pile are qualitatively studied how to influence the utilization of the ultimate bearing capacity of the pile with analytic solution of a load-transfer function in the deep overlay soil layers.It is very much useful for theory and engineering to define the effective length of foundation pile on the basis of the practical request of engineering and reasonable design of pile length because the effective length changes with the load or the settlement of top pileo The definition of effective length of foundation pile is given with comparing and analyzing the definitions by other researchers. Effective lengths of common single pile and pile group are proved from the engineer practice, theory analysis and results of a statically loading test of a single super-pile. By the different methods including the control methods of the ultimate bearing capacity, the settlement of top pile and secant rigidity, the effective length of the pile in deep overlay soil layers is analyzed and calculated with linear elastic-plastic load transfer function. The parameters of influencing effective length and the load-transfer function are thoroughly analyzed. In theory ?factors are perfectly studied how to affect effective length of the pile. Analytic results agree to analytic conclusion with the elastic theory method. In order to apply the suggested methods in practical project, it is studied how to confirm parameters in the project.The paper describes a iterative method to analyze soil-pile-raft interactions and the internal force of raft and axial force of pile and so on are obtained. Computational pile rigidity is relatively reasonable because the reverse force distribution on the top pile and bottom pile of pile group and the interactions between the piles are taken into account = Furthermore, the non-linearity of soiK the layered soils- the nonlinear elasticity of stress-strain relation of concrete pile, and parameter...