This study integrates cross-anisotropic and viscoelastic properties into the solid skeleton of unsaturated soils, conceptualized as a three-phase medium comprising solid, water, and air, in order to explore the torsional response of pipe pile. The stress-strain relationships are characterized using cross-anisotropic and fractional derivative models, resulting in more accurate torsional dynamic equations for the soils surrounding and inside the pipe pile. The torsional governing equations are solved in the frequency domain by applying the separation of variables and leveraging properties of fractional derivatives, while considering boundary continuity conditions and trigonometric orthogonality to derive the pipe pile's torsional complex impedance. The time-domain response to a half-sine excitation load is determined using inverse Fourier transforms and the convolution theorem. After validating the computational model, numerical analyses are conducted to explore the effects of model and geometric parameters on the complex stiffness, twist angle, and torque at the pipe pile head.

This study examines the seismic behavior of a rigid wall in cross-anisotropic poroelastic layered soil, focusing on the frequency domain. Both analytical and numerical solutions are developed to tackle the problem. The analytical solution employs the finite Fourier transform, whereas the numerical solution uses the differential quadrature method. The proposed numerical solution considers various boundary conditions of the wall and base. The results are compared with those of existing studies on elastic soil, encompassing both homogeneous and heterogeneous cases, as well as poroelastic soil. The comparison demonstrates the accuracy of the proposed methods. Notably, the boundary conditions of the wall and base significantly affect the results at specific frequencies. In addition, the layered soil conditions have a relatively significant impact on the results across most frequencies.

The aim of this paper is to propose a two-stage theory-based analytical method for the dynamic performance of pile groups in layered poroelastic saturated cross-anisotropic soils induced by moving loadings. Among them, the free-field vibrational analysis of saturated soils is performed by the analytical element-layer approach (ALEA) and Fourier transformation. Based on the free-field response, the boundary element (BE) solution for the soil resistance at the soil-pile interface is derived utilizing the two-stage theory. Simultaneously, the finite element (FE) solutions for the pile shaft resistance and deformation of pile groups are derived based on the Timoshenko beam theory. Finally, the FE-BE coupled dynamic equation for deformations and internal loadings of the soil-pile system is obtained. Thereafter, the reliability of the proposed method is validated by comparing with existing solutions and FE data from ABAQUS. Based on the derived solutions, a comprehensive parametric study is performed to examine the effects of loading amplitude, force speed, soft soil-layer stiffness, soil anisotropy, and pile length on the dynamic responses of pile groups.

The pile foundations are frequently affected by adjacent traffic loads except for general active loads. However, the dynamic responses of the pile groups under moving loads have been rarely reported before. In addition, the influence of material anisotropy is often neglected. In this paper, a three-dimensional (3D) analytical model for the dynamic analysis of partially buried pile groups in stratified saturated cross-anisotropic media under adjacent moving harmonic loadings is developed. Specifically, a 3D Bernoulli-Euler beam theory is adopted to simulate the monopile and then superimposed into the finite element (FE) formulation for the partially embedded pile groups. Subsequently, the basic solutions of layered saturated cross-anisotropic soils are derived by the analytical layer-element approach (ALEA). By combination with ALEA, the two-stage based boundary element (BE) equations for the pile-soil interface are obtained. Finally, by coupling the FE and BE formulations, the dynamical response equation of pile-soil is established. Based on the verification of the accuracy of the proposed methodology by comparisons with existing solutions and FE results from ABAQUS, the impacts of material anisotropy, pile buried length, loading velocity, and pile stiffness on the time-domain dynamic behavior of pile groups are analyzed. The results show that increasing the pile-buried ratio or pile stiffness reduces the magnitude of the dynamic response. Moreover, with the increase of material anisotropic parameters, the peak pile response decreases. And the peak dynamic response first increases and then reduces as the loading velocity increases.