Passive Redirection of Seismic Waves Through the Use of Gradient Index Metamaterial Barriers

Date: 4/26/2019

Time: 04:00 PM

Room: Pine

Conventional methods of dissipating or absorbing seismic energy come in the form of inertial or resonance-based approaches, such as tuned-mass dampers. This concept has extended to more complex metamaterial designs exploiting the same kinetic-energy physics, such as the ‘Metaforet’ and related soil-mounted approaches. However, in order to dissipate the extraordinary amount of energy present in seismic waves effectively, in the frequency band of interest, very large masses and/or oscillation amplitudes are required.

An alternative passive metamaterial approach would instead redirect the incident waves, rather than absorbing them, using internal energy physics to optimize the elastic properties of the metamaterial design. Optical Gradient index lenses (GRIN lenses) provide a means to redirect light, using regions of differing refractive index. Borrowing this concept, an analogous approach for wave propagation in solids, the acoustic or dilatational GRIN lens can be employed. Acoustic Metamaterial theory provides a design methodology for creating GRIN lenses; such metamaterial lenses redirect seismic waves away from structures of interest, reducing ground vibration levels considerably.

Mitigation of various solid waves and the design concepts behind geo-scale acoustic metamaterials is discussed, with numerical experiments effected through the finite element software PZFlex. Discussion of some current mitigation technologies that would be augmented / supplanted by a notional metamaterial, if successful, will be provided to establish context for the development of a practical metamaterial-based solution.

Presenting Author: Andrew J. Shakalis

Authors