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

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.