Forest Trees as Natural Metamaterial to Mitigate Railway-Induced Ground Vibrations

Abstract

Forest trees as a natural metamaterial provide advantages in terms of low cost and environmental sustainability when addressing train-induced ground vibrations. This study proposes a three-dimensional semi-analytical method developed for evaluating the dynamic responses of the coupled track-ground-tree system. The thin-layer method is employed to derive an explicit Green’s function corresponding to a harmonic point load acting on a layered half-space, and subsequently applied to couple the foundation with the track system. The forest trees are modeled as surface oscillators coupled on the ground surface to evaluate the characteristics of the multiple scattered wavefield. The vibration attenuation capacity of forest trees in mitigating railway-induced ground vibrations is systematically investigated using the proposed method. In the direction perpendicular to the track on the ground surface, a graded array of forest trees with varying heights is capable of forming a broad attenuation zone at frequencies below 80 Hz. Due to the interaction of wave fields excited by harmonic point loads at multiple locations, the attenuation performance of the tree system varies significantly across different positions on the surface. The influence of variability in tree height, radius, and density on system performance is subsequently examined using a Monte Carlo simulation. Despite the inherent randomness in tree characteristics, the forest still demonstrates notable attenuation effectiveness at frequencies below 80 Hz. Among the considered parameters, variations in tree height exert the most pronounced effect on the uncertainty of attenuation performance, followed sequentially by variations in density and radius.

Keywords: Railway-induced vibration attenuation, Three-dimensional semi-analytical modelling, Metamaterials, Forest trees, Monte Carlo simulation