Theoretical Study On Horizontal Vibration Of Pile-Soil-Water Coupling System Under Complex Conditions

The elevated piles have been widely applied in harbor engineering and offshore engineering.The piles are always subjected to horizontal dynamic loading caused by wind,wave,earthquake and vertical loading from super structure.The soil properties adjacent to the foundation usually change due to construction disturbance and degradation of modulus under cyclic loading.Besides,the pile part above the ground surface of elevated piles in harbor engineering and offshore engineering is surrounded by water.How the pile-water interaction affects the horizontal dynamic response of pelevated piles is still not clear.It is of great significance to investigate the horizontal dynamic behavior of elevated piles in saturated soil,considering complexity of loading,radial inhomogeneity of soil and dynamic interaction between pile and water.Firstly,based on the theory of saturated porous media,the dynamic behavior of elevated piles under horizontal dynamic loading and vertical loading is analyzed.Then,the analytical model considering dynamic pile-water interaction is proposed,and the effect of dynamic pile-water interaction on horizontal dynamic response of elevated piles is investigated.The main work and research results of this paper are as follows:(1)Based on the Biot's poroelastic theory,an analytical model is proposed to investigate the horizontal dynamic response of an elevated pile in saturated soil layer which subjected to combined horizontal and vertical loading.The saturated soil is described by Biot's poroelastic theory and resistance of the soil is derived by potential function method.The governing equation of the soil and pile is solved by potential function method and separated variable method,and the analytical expression of impedance of the pile is obtained.Finally,a parametric study is carried out to investigate the effects of soil properties,length of pile part above soil surface and vertica loading on the horizontal dynamic impedance and horizontal dynamic response of the pile.(2)To account for the radial inhomogeneity of surrounding soil caused by construction disturbance and cyclic softening,a continuous variation of soil property in radial direction is assumed.The soil layer is divided into finite concentric annular zones.Based on the continuity conditions at the interface of the adjacent zones,the horizontal resistance of radially inhomogeneous soil layer is obtained by utilizing transfer matrix method.Then,the horizontal dynamic impedance of pile is obtained by solving the dynamic equilibrium equation of the pile.Finally,a parametric study is performed to investigate the influence of radial inhomogeneity of saturated soil on the horizontal impedance of soil and impedance of pile.It is revealed that disturbance degree and disturbance range of surrounding soil have significant influence on the horizontal impedance of soil and impedance of pile.(3)Based on the model of radially multi-zone inhomogeneous soil,an analytical model is proposed to investigate the horizontal dynamic behavior of pile foundations in layered saturated soils considering radial inhomogeneity.The horizontal resistance of radially inhomogeneous soil layer is obtained by utilizing transfer matrix method.Then,the governing equation of the pile is solved by coupling the soil resistance and the continuity between the pile and the soil,and the impedance of pile is obtained by utilizing transfer matrix method.Finally,a parametric study is performed to investigate the influence of radial inhomogeneity of saturated soil on the impedance of pile.(4)An analytical model is proposed to investigate the horizontal dynamic response of an elevated pile in water and the dynamic pile-water interaction is considered.The governing equation of water is solved based on the separation variable method,and the analytical expression of hydrodynamic force applied on the pile is then obtained.Based on the continuous conditions at pile-soil interface and pile-water interface,the governing equation of the pile is solved and impedance of the pile is obtained.Based on the presented solution,the effect of hydrodynamic pressure and other parameters on horizontal dynamic impedance and dynamic response of elevated pile in water is investigated.(5)Considering dynamic pile-inner water interaction and pile-inner soil interaction,the horizontal dynamic response of a pipe pile in water is investigated.The governing equation of inner water and inner soil are solved based on the separation variable method,and the analytical expression of hydrodynamic pressure of inner water and resistance of inner soil are obtained.Based on the continuous condition at the pile-inner soil interface and pile-inner water interface,the analytical solution of for dynamic response and impedance of pipe pile in water is derived via transfer-matrix formulation.Based on the presented solution,the influence of inner water,water depth,inside radius and inner soil on impedance of pipe pile in water is investigated.