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The application of metamaterial in civil engineering to achieve isolation of a building by controlling the propagation of seismic waves is a substantial challenge because seismic waves, a superposition of longitudinal and shear waves, are more complex than electromagnetic and acoustic waves. In this paper, we design a broadband seismic metamaterial based on H-shaped fractal pillars and report numerical simulation of band structures for seismic surface waves propagating. Comparative study on the band structures of H-fractal seismic metamaterials with different levels shows that a new level of fractal structure creates new band gap, widens the total band gaps and shifts the same band gap towards lower frequencies. Moreover, the vibration modes for H-fractal seismic metamaterials are computed and analyzed to clarify the mechanism of widening band gaps. A numerical investigation of seismic surface waves propagation on a 2D array of fractal unit cells on the surface of semi-infinite substrate is proposed to show the efficiency of earthquake shielding in multiple complete band gaps.

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Controlling the propagation of seismic waves to protect critical infrastructure via metamaterial is of new topical interest. This approach can be implemented by remote shielding of incoming waves rather than with vibration isolating structures. In this paper, a two-dimensional elastic metamaterial with periodically square concrete-filled steel piles embedded in soil is proposed to achieve a seismic shield for guided Lamb waves and surface waves. Its properties are numerically investigated using the finite element method. For Lamb waves, we first identify complete bandgaps appearing in a periodic composite with cylindrical piles. By comparison, it is found that if the shape of the pile is replaced with the square shape, the bandgaps become wider and shift to the lower frequencies, which is more suitable for practical applications. Furthermore, it is demonstrated that a complete low frequency bandgap also exists for surface waves. The vibration modes for both types of waves at the bandgap edges are computed and analyzed to clarify the mechanism of the bandgap generation. The study focuses on realistic structures that can be effective in the frequency ranges for seismic waves. Although we have focused on the geophysical setting, elastic waves are also very important in applications involving acoustic wave devices.

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A novel seismic metamaterial plate consisting of two common building materials, which has the advantages of simple structure and easy to realize, is proposed. The seismic metamaterial plate creates a wide bandgap with a relative bandwidth of 1. Using numerical simulation, the bandgap properties of the metamaterial plate both in a free space and on a half space are studied and it is found that the wide bandgap of the free plate is kept even if in half space. Using scaled (1:30) experiments under 1 g conditions and simulations, we study the transmission spectrum under the surface waves incident on the seismic metamaterial plate and verify that it has a good attenuation effect in the corresponding frequency range. This work paves the way to the design of seismic metamaterials allowing an unparalleled control of surface wave propagation.