Forests as a natural seismic metamaterial: Rayleigh wave bandgaps induced by local resonances.
Forests as a natural seismic metamaterial: Rayleigh wave bandgaps induced by local resonances.
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DOI：
10.1038/srep19238
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发表时间：
2016-01-11
影响因子：
4.6
通讯作者：
Craster RV
中科院分区：
文献类型：
--
作者：
Colombi A;Roux P;Guenneau S;Gueguen P;Craster RV
我们探讨了这样的论点：树木的共振导致森林在地球物理背景下充当瑞利表面波的局部共振超材料。地球物理实验表明，瑞利波在软沉积土中以低于 150Hz 的频率传播，当与森林相互作用时，瑞利波会在两个独立的大频带上经历强烈的衰减。该实验使用有限元模拟进行解释，表明当树木相对于入射瑞利波以亚波长尺度排列时，观察到的衰减是由带隙引起的。重复的带隙是由树木的连续纵向共振与瑞利波的垂直分量耦合产生的。对于低至 5 米的波长，当树木的声阻抗与土壤的阻抗相匹配时，产生的带隙非常大并且强烈衰减。由于垂直谐振器的纵向谐振与其长度成反比，因此可以从耦合到地面的纵向谐振≤10Hz的垂直柱开始，设计一个人造工程谐振器阵列，以衰减频率≤10Hz的瑞利波。
We explore the thesis that resonances in trees result in forests acting as locally resonant metamaterials for Rayleigh surface waves in the geophysics context. A geophysical experiment demonstrates that a Rayleigh wave, propagating in soft sedimentary soil at frequencies lower than 150 Hz, experiences strong attenuation, when interacting with a forest, over two separate large frequency bands. This experiment is interpreted using finite element simulations that demonstrate the observed attenuation is due to bandgaps when the trees are arranged at the sub-wavelength scale with respect to the incident Rayleigh wave. The repetitive bandgaps are generated by the coupling of the successive longitudinal resonances of trees with the vertical component of the Rayleigh wave. For wavelengths down to 5 meters, the resulting bandgaps are remarkably large and strongly attenuating when the acoustic impedance of the trees matches the impedance of the soil. Since longitudinal resonances of a vertical resonator are inversely proportional to its length, a man-made engineered array of resonators that attenuates Rayleigh waves at frequency ≤10 Hz could be designed starting from vertical pillars coupled to the ground with longitudinal resonance ≤10 Hz.