Vibration isolation effects of pile barriers in layered saturated transversely isotropic foundations under moving loads

The vibration isolation effects of pile rows in saturated layered transversely isotropic soils due to moving loads are evaluated using the finite-element-boundary-element coupled method. The finite element matrix equations for the pile are obtained based on the Bernoulli-Euler beam theory by discretizing the pile rows into single piles and pile units using the finite element method. At the pile-soil boundary, the soil and pile units are discretized with equal nodes, and the analytical layer-element basic solution for the layered transversely isotropic saturated foundation consolidation problem is used as the kernel function to obtain the flexibility matrix using the boundary integral method. Further, based on the two-stage theory, the influences of lateral friction resistance and the vibration directly caused by the moving loads are coupled, and the boundary element equations are obtained by combining the boundary element method. The displacement coordination conditions of no relative slip and dislocation between the piles and the soils are used to couple the finite element and boundary element equations, and the dynamic response equation for the pile rows is obtained. Then, the displacement of an observation point after the pile rows without and with the pile vibration isolation is calculated separately, and the isolation efficiency is obtained by combining with the vibration isolation theory. The accuracy of the proposed method is verified by comparing with the existing numerical results, and the effects of the load velocity and different pile materials on the vibration isolation effects are analyzed. The results show that two times the Rayleigh wavelength is the optimal pile length, and the vibration isolation effects will not improve greatly beyond the critical value. The greater the difference in stiffness between the pile and foundation, the better the vibration isolation effects. When the load speed exceeds the shear wave speed, the vibration isolation performance