Journal
INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
Volume 154, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijengsci.2020.103347
Keywords
Metamaterials; Rayleigh waves; Biot's theory; Fluid-solid interaction; Band gaps
Categories
Funding
- European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska Curie [813424]
- University of Bologna - DICAM
- National Natural Science Foundation of China [51878030, 51878031]
- Beijing Natural Science Foundation [8182045]
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Seismic surface wave mitigation using metamaterials is a growing research field propelled by intrinsic theoretical value and possible application prospects. Up to date, the complexity of site conditions found in engineering practice, which can include layered stratigraphy and variable water table level, has been discarded in the development of analytical frameworks to favor the derivation of simple, yet effective, closed-form dispersion laws. This work provides a further step towards the analytical study of seismic metasurfaces in real site conditions considering the propagation of Rayleigh waves through a layered porous substrate equipped with local resonators. To this aim, we combine classical elasticity theory, Biot's poroelasticity and an effective medium approach to describe the metasurface dynamics and its coupling with the poroelastic substrate. The developed framework naturally includes simpler configurations like seismic metasurfaces atop homogeneous dry or saturated soils. Apart from known phenomena like wave-resonance hybridization and surface wave band gaps, we predict the existence of an extended frequency range where surface waves are attenuated due to energy leakage in the form of slow pressure waves, as a result of the fluid-solid interaction. Besides, we demonstrate that the surface wave band gap and the related surface-to-shear wave conversion is robust to variations in the water table level. Conversely, when the dry and saturated layers have different material parameters, for example, due to different porosity ratios, the surface-to-shear wave conversion can be accompanied by the excitation of higher-order surface modes, which remain channeled below the metasurface. These analytical findings, augmented and confirmed by numerical simulations, evidence the importance of accounting for fluid-solid interaction in the dynamics of seismic metasurfaces. (C) 2020 Elsevier Ltd. All rights reserved.
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