Abstract
The low frequency of seismic waves severely limits the regulation of wave propagation in earthquake protection engineering applications. In recent years, locally resonant metamaterials have been introduced for seismic wave attenuation. A barrier based on locally resonant metamaterials consisting of rows of wells is proposed to reduce the transmission of Rayleigh waves during propagation, achieving earthquake protection. First, comparisons are made between the wells of the metamaterial, empty wells, solid steel wells, and a continuous steel wall. It is evident that locally resonant metamaterials exhibit better performance than that of the other materials. Simulations of the relationships between the attenuation of Rayleigh waves and the depth, number of rows, and working frequency of the wells are presented. With a barrier of ten rows of wells, where the diameter of each well is less than one-twentieth of the wavelength of the Rayleigh wave and the depth of the wells is nearly four-fifths of the wavelength, the maximum attenuation reaches up to 16.2 dB when all the wells share the same working frequency, and the bandwidth is broader, but the maximum value is less when the rows have different working frequencies. Depending on the demand for a higher value or a broader bandwidth of the Rayleigh wave attenuation, this barrier promotes flexible and achievable improvements by adding rows or decentralizing the working frequencies of the wells. The vast potential of seismic wave attenuation from locally resonant metamaterials is anticipated in the future.
Highlights
The idea of a metamaterial was first introduced in electromagnetism, such as an electromagnetic absorber to stop the propagation of electromagnetic waves in certain frequency regimes.1–3 Many researchers have attempted to find acoustic or elastic metamaterials possessing similar properties
We have developed a barrier of locally resonant metamaterials for Rayleigh wave attenuation
The barrier consists of rows of wells filled with locally resonant structures to present an apparent dynamic mass density
Summary
The idea of a metamaterial was first introduced in electromagnetism, such as an electromagnetic absorber to stop the propagation of electromagnetic waves in certain frequency regimes. Many researchers have attempted to find acoustic or elastic metamaterials possessing similar properties. To seek a more effective solution for Rayleigh wave attenuation at a low frequency, we propose an artificial barrier consisting of a formation with rows of wells. These wells present an apparent dynamic mass density that is different from a static mass such as a solid steel well. There are gaps between the two wells in a row, which distinguishes this barrier from a continuous underground wall Such a setting has the advantage that the locally resonant metamaterial effects the attenuation of a Rayleigh wave without completely blocking the propagation path, such as with a wall in the following examples.
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