Low-frequency broadband seismic metamaterial using I-shaped pillars in a half-space

In this paper, a new type of low-frequency broadband elastic metamaterial is proposed, which is constituted of periodic I-shaped pillars arranged on a two-dimensional ground surface. The propagation of elastic waves through 3D samples of the seismic metamaterial is investigated in the harmonic regime by a combination of the finite element method and Bloch theory. In contrast, with two typical pillar structures consisting of circular and rectangle pillars, the proposed I-shaped seismic metamaterial can yield wider bandgaps and significantly attenuate the seismic surface waves at the frequencies ranging from 5.8 Hz to 8.8 Hz and from 9.2 Hz to 13.0 Hz, respectively. The generation mechanism of the bandgaps is further explored by computing the transmission spectra through a finite array and analyzing the displacement fields of the surface at 6.1 Hz and 10.2 Hz in two different bandgaps. The optimal geometric parameters of the I-shaped seismic metamaterial are also provided. Although we focus on the geophysical structure, the proposed metamaterial provides a possible alternative for various phenomena such as vibration and noise attenuation because the center frequencies of bandgaps can be easily achieved by modulating the material and geometrical parameters.