层状地基中海洋大直径管桩水平动力响应分析

Behavior of large-diameter pipe piles in offshore layered soils under lateral dynamic loading

考虑桩−海水−层状土相互作用,研究了水平动荷载作用下层状地基中海洋大直径管桩的动力响应特性。将海水视为无黏性可压缩流体介质建立桩周、桩芯海水的运动方程,通过分离变量法并结合海水的边界条件求得桩周、桩芯海水作用在管桩上的动水压力。将海床土体视为黏弹性介质并考虑其成层非均质性,利用微分变化并结合土体振动边界条件解得桩周、桩芯土体作用在管桩上的水平抗力。进而根据各桩段上水平力的平衡建立管桩控制方程,利用传递矩阵法并结合桩身的连续条件以及桩顶、桩底的边界条件,得到层状海床土中海洋大直径管桩的水平动力响应解析解,给出了桩顶位移解析表达式。将所得解与有限元模拟结果以及退化解与已有文献解进行对比,验证了本研究计算方法的合理性。并基于所得解分析了管桩−海水−层状土系统水平动力响应对动水压力、水深、土体模量、土层厚度等关键参数的敏感性。

The study investigates the dynamic response characteristics of offshore large-diameter pipe piles in layered seabed soil under horizontal dynamic loading,considering the interaction between pipe piles,seawater,and layered seabed soil.Seawater is treated as an inviscid compressible medium to establish the motion equations of outer and inner seawater.The hydrodynamic pressure of outer and inner seawater acting on the offshore pipe piles is derived using the separation variable method and combined with the boundary conditions.The seabed soil is considered as a viscoelastic medium,and its layered nonhomogeneity is simultaneously taken into account.The horizontal resistances of outer and inner seabed soil acting on the pipe piles are derived using the differential variation method in conjunction with the vibrational boundary conditions.The governing equation of the pipe pile is established based on the balance of horizontal force on each pile section.The analytical solution of the horizontal dynamic response of offshore large-diameter pipe piles in layered seabed soil is derived using the transfer matrix method and combined with the continuity condition of pile piles and the boundary conditions of pile head and bottom.Analytical expression of pile head displacement is also obtained.The proposed solution’s results are validated against FEM numerical results and existing analytical solutions to verify its rationality.Finally,based on the presented solution,the sensitivity of the horizontal dynamic responses of the pipe pile-water-layered soils system to certain key parameters,such as hydrodynamic pressure,water depth,soil modulus,and soil layer thickness,is analyzed.