Vibration mitigation in saturated soil by periodic pile barriers

Coupling the widely used Biot's theory and the periodic structure theory in the solid-state physics, this paper presents a comprehensive numerical investigation on the complex dispersion properties of periodic pile barriers and further explores the vibration mitigation properties of periodic pile barriers in the frequency domain. In particular, using the fluid-saturated poroelastic medium model the influences of the fluid viscosity on the vibration attenuation property of pile barriers are investigated. It is found that the real frequency bands of the pile barriers can be classified as three categories: high-speed longitudinal-wave bands, low-speed longitudinal-wave bands, and shear-wave bands. The shear-wave directional attenuation zones (SDAZs) obtained by the complex dispersion analysis are broader than those obtained by the traditional real dispersion analysis. Attenuation zones for different wave modes can be identified easily based on the present method. Further, the effects of the soil skeleton, the soil permeability, the fluid viscosity, as well as the geometric parameters of the pile barriers on the complex dispersion and the SDAZs are deeply discussed. Frequency response analysis of a periodic pile system is conducted to validate the efficiency of the SDAZs. The findings of this study present a proper way to design periodic pile barriers in saturated soil for ambient vibration attenuation.