Collaborative enhancement isolation of railway-induced vibrations by composite metamaterial surface wave barrier

To achieve broadband environmental vibration control in rail transit and address the limitations of single-mechanism barriers, suffering from either narrow bandwidth or oversize and complex structures, a novel periodic composite metamaterial barrier integrating Wave Impeding Blocks (WIBs) and in-filled trenches is proposed. This barrier realizes synergistic coupling of Bragg scattering and local resonance bandgaps (BGs). Experimental model tests are conducted to investigate the vibration isolation and reduction performance of the barrier structure, and the results are mutually verified with finite element results. The finite element method is further used to analyze the band structure and vibration transmission characteristics of the barrier. The formation mechanism of the BG is interpreted through modal shapes and displacement field distributions, and the dynamic responses under the individual and combined loads of subway and high-speed train at Wuhan Station are studied. The results show that the synergistic effect of the proposed composite structure, with a 0.2 m square side, can significantly modulate the bands to approach flat bands, generating an ultra-wide BG with a starting frequency as low as 10 Hz within the frequency range below 80 Hz. It exhibits good suppression of rail transit vibrations, with the maximum peak acceleration reduction reaching 88%. This is because part of surface waves are localized in the resonant units, and the other part is converted into bulk waves that propagate away from the ground surface. The research results provide a new design idea for the application of periodic surface wave barriers in ultra-low-frequency vibration isolation and reduction.