Seismic metamaterials

International audienceThis document presents the description of a preliminary large-scale seismic test held on a soil metamaterial using vibrocompaction probes. The most simplistic way to interact with seismic wave is to modify the global properties of the medium, acting on the soil density and then on the wave velocity. The main concept is then to reduce the amplification of seismic waves at the free surface, called « site effects » in earthquake engineering. However, we develop here an other way to counteract the seismic signal by modifying the distribution of the seismic energy thanks to a " metamaterial " made of a grid of vertical, cylindrical and empty " inclusions " bored in the initial soil. Site effect: The amplification of seismic waves at the free surface, namely « site effects » may strengthen the impact of an earthquake in specific areas (e.g. Mexico 1985). Indeed, when seismic waves propagate through alluvial layers or scatter on strong topographic irregularities, refraction/scattering phenomena may strongly increase the amplitude of the ground motion. It is then possible to observe stronger motions far away from the epicenter. At the scale of an alluvial basin, seismic effects involve various phenomena as wave trapping, resonance of the whole basin, propagation in heterogeneous media, generation of surface waves on the basin edges