Experiment on broadband isolation of surface wave using pillared metastructures

It is challenging to achieve broadband isolation of ground vibration. In this work, pillared metastructures are proposed for broadband vibration isolation of surface wave in sandy soil numerically and experimentally. We first investigate two kinds of pillared metastructures, namely the pillars exposed on top of the soil or partially embedded in soil. Numerical and experimental results show that the case of partially embedded pillar has a wider and higher bandgap. Then we study gradient metastructures with linear or non-linear distributions of embedded depths, resulting in lower and wider attenuation frequency ranges, which are also validated by experiments. It is shown that gradient metastructures with a fixed ratio of bandgap overlaps to adjacent bandwidths have a greater advantage in low-frequency isolation. Our study provides great inspiration for simple design and manufacturing of new seismic metastructures to reduce surface waves or vibrations.