Mitigation of Rayleigh-like waves in granular media via multi-layer resonant metabarriers

TL;DR

This study explores how multi-layer resonant metabarriers can effectively attenuate Rayleigh-like surface waves in granular media, combining experiments and simulations to demonstrate enhanced wave mitigation.

Contribution

It introduces a novel multi-layer resonator design that significantly improves surface wave attenuation in granular media compared to single-layer configurations.

Findings

Multi-layer resonator arrays increase wave attenuation.

Wavefronts are back-scattered and redirected downward.

Additional layers broaden the attenuation band.

Abstract

In this work, we experimentally and numerically investigate the propagation and attenuation of vertically polarized surface waves in an unconsolidated granular medium equipped with small-scale metabarriers of different depths, i.e., arrays composed of one, two, and three embedded layers of sub-wavelength resonators. Our findings reveal how such a multi-layer arrangement strongly affects the attenuation of the surface wave motion within and after the barrier. When the surface waves collide with the barriers, the wavefront is back-scattered and steered downward underneath the oscillators. Due to the stiffness gradient of the granular medium, part of the wavefield is then rerouted to the surface level after overcoming the resonant array. Overall, the in-depth insertion of additional layers of resonators leads to a greater and broader band wave attenuation when compared to the single layer case.