Research On Analytical Method Of Time Effect Of Vertical Loaded Pile Settlement

In order to accurately calculate and predict the time-dependent settlement of pile foundations,and then serve the design of pile foundations,this dissertation systematically studies the time effect of single pile settlement and pile group settlement under vertical load in homogeneous and layered soil respectively by means of theoretical analysis,and establishes the computing methods for time-dependent settlement of pile foundations.The main work is summarized as follows:(1)Based on the one-dimensional fractional derivative Merchant viscoelastic model,the three-dimensional model is deduced to describe the rheological properties of the soil around the pile.According to the shear deformation coordination between the pile and the soil,the equilibrium and boundary equations are established,and the semi-analytical solution for time-dependent settlement of single piles in homogeneous soil is obtained by using the Laplace transform technique and correspondence principle.The computing method for time-dependent settlement of single piles in homogeneous soil is proposed,and the accuracy and effectiveness of the method are verified by comparison with two examples.The influence of six main parameters a-G1/G2,b=η/(G2tc),c=G1/K,d=G1/Ep,k＝L/r0 and a on the time-dependent settlement of single pile under three typical loading modes(instantaneous loading,ramp loading and progressive loading)is analyzed in detail(2)Based on the computing method for time-dependent settlement of single piles in homogeneous soil,the interaction coefficient method is introduced to consider the pile-pile interaction in pile groups.On this basis,the interaction factors between different pile sides and different pile tips are obtained respectively by considering the reinforcement effect of adjacent piles,and the computing method for time-dependent settlement of pile groups in homogeneous soil is proposed,and the accuracy and effectiveness of the method are verified by comparison with an example.The influence of the slenderness ratio k and the pile spacing r on the interaction factor and the time-dependent settlement of three typical pile groups(2×1 pile group,2×2 pile group and 3×1 pile group)under the instantaneous loading are analyzed in detail respectively.(3)Based on the computing method for time-dependent settlement of single piles in homogeneous soil,the influence of layered soil around the pile on the time-dependent settlement is considered by introducing the soil non-uniform coefficients on pile side and pile tip respectively,and the computing method for time-dependent settlement of single piles in layered soil is proposed,and the accuracy and effectiveness of the method are verified by comparison with three examples.The influence of the nonuniform coefficient of the soil on the pile side the pile tip on the time-dependent settlement of single pile under three typical loading modes(instantaneous loading,ramp loading and progressive loading)is analyzed in detail respectively.(4)Based on the computing method for time-dependent settlement of pile groups in homogeneous soil,the influence of layered soil around group piles on the interaction factor and the time-dependent settlement of group piles is considered by introducing the soil non-uniform coefficients on pile side and pile tip respectively,and the computing method for time-dependent settlement of pile groups in layered soil is proposed,and the accuracy and effectiveness of the method are verified by comparison with two examples.The influence of the coefficient of non-uniformity of soil on pile side and pile tip on the interaction factors and the time-dependent settlement of pile groups are analyzed in detail respectively.