Ultra-low-frequency broadband characteristics of radial gradient supercell seismic metamaterials

Abstract

This study aims to discuss the propagation characteristics of seismic Lamb wave and surface wave in a new radial gradient supercell seismic metamaterial (RGSSM). Different from the traditional seismic metamaterials with simple unit cells, the RGSSM consists of the supercells arranged periodically along the radial direction, and these supercells are composed of five kinds of unit cells with gradient filling rates. The dispersion curve and attenuation spectrum of the Lamb wave in RGSSM are studied with the finite element method combined with the supercell technology, generating a very low-frequency ultra-wide bandgap of 3.98-20 Hz, and a forbidden band generated by the localized modes forms multi-harmonic oscillators inside the supercell. Furthermore, it is found that the Young’s modulus of the soil is more sensitive to the effect of bandgap. In terms of surface wave, the RGSSM can produce rapid attenuation in the low frequency range of 5.2-8.5 Hz. Finally, a 3D model is designed to demonstrate the shielding performance of RGSSM against the seismic surface wave. The proposed RGSSM provides a new idea for the seismic isolation of ultra-wide and low-frequency seismic waves.

Keywords

radial gradient supercell seismic metamaterials(RGSSM) / supercellular method / ultra-low-frequency broadband

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