Investigating the damping performance and multi-mechanism superposition effects of helical beam oscillator-type seismic metamaterials

Attenuating ultra-low-frequency seismic surface waves (starting frequencies close to 0 Hz) through structural design in confined spaces is a pressing issue. This paper proposes a novel seismic metamaterial (SM) composed of periodically arranged iron box components encased in soil, with helical beam vibrators embedded as resonators to dissipate energy. By combining dispersion analysis and acoustic cone methods, parameter and frequency-domain analyses were conducted on the seismic metamaterial, demonstrating a zero-frequency band gap ranging from 0 to 16.34 Hz under quasi-Dirichlet conditions. While changes in structural parameters minimally affect the width of the zero-frequency band gap, their attenuation effect will significantly vary with the changes in parameter under different mechanisms. This finding suggests that the superposition of multiple mechanisms, such as local resonance and reverse dispersion, effectively creates ultra-low-frequency, high-loss band gaps. Time-domain analysis further validated the effectiveness of the study. The results indicate that multiple damping mechanisms can be superimposed within a specific range, thus enhancing the shielding effect of seismic metamaterials against seismic waves. This research is expected to promote the engineering application of common building materials in shielding seismic waves at deep sub-wavelength frequencies.