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

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