Seismic metamaterials for Rayleigh wave attenuation: A novel concept of soil-embedded water-tank metabarrier

In the context of ongoing research on seismic metamaterials, this paper proposes a novel metabarrier for seismic Rayleigh wave attenuation, conceived as a periodic array of soil-embedded cylindrical water tanks acting as resonant units below the soil surface. A theoretical framework is developed, where the dynamics of the water tank is treated by a classical 3D linear, pressure-based model for fluid-structure interaction under earthquake and the soil is idealized as homogeneous and isotropic medium, in agreement with similar studies on seismic metamaterials. The dispersion diagram obtained from the Floquet–Bloch dispersion analysis exhibits relevant band gaps in the low frequency range of seismic Rayleigh waves, as well as in the higher frequency range of Rayleigh waves caused by other ground vibration sources as, e.g., railway or road traffic. Frequency-domain analyses of a soil domain with a finite array of water tanks validate the band gaps and show considerable attenuation. An appealing feature of the proposed metabarrier is that the water-tank resonant units can be tuned by varying the water level; indeed, it is shown that, in this manner, opening frequencies and sizes of the band gaps can be changed. This is a remarkable advantage over alternative seismic metamaterials that, in general, are not designed to be tunable. All calculations are implemented in COMSOL Multiphysics.