Horizontal Transient Dynamic Response Of Pipe Pile In Saturated Soil

Pipe piles are widely used in many engineering areas such as bridge projects,high-rise buildings and offshore platforms as an important basic form due to their advantages such as high bearing capacity of single pile,good bending resistance,good seismic performance,stable and reliable quality,and fast construction speed.Under dynamic loading,the stability of the pile foundation depends on the working performance of the pile,and the working performance of the pile foundation is the result of the dynamic interaction between the pile and its surrounding soil,and due to the hollow nature of the pipe pile,its stress characteristics are different from that of a solid pile.At present,the research on transient response of pile foundation is limited to single-phase medium.However,soil is a three-phase medium consisting of solid,liquid,and gas.It is undoubtedly that research on saturated two-phase medium is closer to objective reality and has more practical value.The research on the transient response of pile foundation level is not mature.Therefore,the horizontal transient response of pipe piles in saturated heterogeneous soils was studied.This article is divided into six chapters,mainly to do the following work:1.Based on two-parameter Pasternak model,the horizontal transient dynamic response of pipe pile in layered soils with partial head fixity is theoretically investigated without considering inner soil.The relation between the moment and rotation of the pile head is assumed to be two-stage equivalent linear model.By applying the matrix transfer method,the relationship of the state variables between the arbitrary pile segment and pile top is established,and then the time domain solution of pile top under horizontal transient loading is derived through Laplace transformation and its numerical inversion.2.Based on the 3D motion equation,considering both the outer and inner soils,the horizontal transient time-domain response of Timoshenko model pipe pile in isotropic saturated soil is investigated.Firstly,the potential function is introduced to decouple the soil dynamic consolidation equation.The lateral force of the outer and inner soils is obtained combining the initial boundary condition by means of operator decomposition and separation of variables.According to the assumption of perfect contacts between the pile and both the outer and inner soils as well as the formula of Laplace inverse transform,the time domain solution of the displacement and internal force of the pile is derived with different pile-head restraint.3.Based on the continuous medium model,the transient vibration characteristics of pipe piles in radial heterogeneous saturated soil are studied.Firstly,the soil around the pile is equivalent to the radial heterogeneous inner layer near the pile and the homogeneous outer layer far from the pile,and the internal disturbed soil is further divided into the areas of thin concentric rings.Each lap is considered as homogeneous soil.Then,the equation of the saturated soil and the dynamic balance equation of the pile body are established for each layer of soil.According to the boundary conditions and continuous contact conditions,the time domain solution of the displacement and internal force of the pile in the radial heterogeneous soil is derived.4.Based on the plane strain model,the horizontal dynamic characteristics of pipe piles in longitudinally two-way heterogeneous saturated soil layers are studied.Firstly,according to the longitudinal layering of the soil around the pile,it is divided into multiple layers along the longitudinal direction,and then each layer in the longitudinal direction is equivalent to the homogeneity of the radially inhomogeneous multi-circle inner layer soil and the outer layer soil of the distant pile.Each layer is considered as homogeneous soil.Then,the wave equation of each layer of soil and the dynamic balance equation of each pile are established.Combined with the boundary conditions and continuous contact conditions,analytical expressions for the complex impedance of the pile top in longitudinal heterogeneous biaxial heterogeneous soils are given.The comparison with existing examples verifies the correctness of the derivation.