Narrow Results

An analytical approach is proposed for analyzing the horizontal dynamic response of an offshore pile, considering the soil as a saturated porous medium with radial heterogeneity, and accounting for the dynamic pile–water interaction. The soil is divided radially into two zones: a homogeneous outer zone and a heterogeneous inner zone consisting of finite concentric annular sub-zones. The horizontal resistance of the radially inhomogeneous soil layer is determined using the transfer matrix method. Subsequently, by utilizing the calculated soil resistance and the hydrodynamic force acting on the pile, the solution for the horizontal vibration of the pile is derived. The accuracy of the proposed approach is validated through comparisons with results from previous studies. Furthermore, a parametric study is conducted to explore the horizontal dynamic response of offshore piles within radially inhomogeneous saturated soil. The investigation demonstrates that the horizontal dynamic response of offshore piles is significantly influenced by the level of soil disturbance, range of disturbance zone, soil permeability, and water depth.

The torsional dynamic response of a pile embedded in transversely isotropic saturated soil is investigated while allowing for the construction of disturbance effect. The dynamic governing equations of soil are established based on Biot’s poroelastic theory. By virtue of the continuous conditions of stress and displacement of adjacent disturbance circle and the boundary conditions of pile-soil coupling system, the circumferential displacement of soil and the shear stress on pile-soil contact surface are derived. Subsequently, a closed-form solution for the torsional dynamic response of a pile is derived in the frequency domain. By using inverse Fourier transform and the convolution theorem, a quasi-analytical solution for the velocity response of the pile head subjected to a semi-sine excitation torque is derived in the time domain. The proposed analytical solution is verified by comparing with the two existing solutions available in literature. Following the present solution, a parameter study is undertaken to portray the influence on the complex impedance, twist angle and torque of pile.

Characteristics of localized behavior of saturated soil with pore water is examined via Element-Free Galerkin (EFG) method while comparing with the FEM solutions under elasto-plastic constitutive equation. A set of weak forms of the nominal stress rate for soil skeleton and the continuity of pore water is derived for the field of finite deformation. An example problem concerning the triaxial test is dealt with where numerical difficulties are appeared in the computation. The mesh-free method provides the wellposed solution for this type of problem while overcoming the mesh dependency of the localization of the test specimen.