Surface Wave Attenuation by Periodic Pile Barriers in Unsaturated Soil

Due to their attenuation zone characteristics, underground periodic barriers such as row piles used to isolate surface wave propagation in soil have been attracting increasing attention in recent years. However, most existing studies have been conducted in single-phase or saturated soils, while investigations in unsaturated soils remain scarce. Among the limited work in unsaturated soils, periodic in-filled trench barriers have been primarily investigated for surface wave isolation, whereas periodic pile barriers have mostly been applied to bulk wave isolation. To fill this gap, this study systematically investigates the effect of periodic pile barriers in unsaturated soil to attenuate surface waves. By establishing a three-dimensional finite-element model, the complex dispersion relations of a periodic pile barrier in unsaturated soil for surface waves are solved, and the attenuation mechanism of the barrier is uncovered. Two surface wave attenuation zones, in the frequency ranges of 44.5–54 and 60–70 Hz, are observed for the periodic pile barrier considered in this study. Subsequently, the performance of periodic pile barriers in mitigating surface wave propagation is studied through both frequency and time domain analyses. Finally, a detailed discussion is carried out on the impacts of a few important parameters of unsaturated soil on the attenuation zone and isolation effect of this wave barrier. It is discovered that the change of saturation has a significant influence on the results and that the surface waves would be isolated over the whole frequency range when the intrinsic permeability is within a certain range. This research offers a new perspective on the control of surface wave propagation by periodic pile barriers.