Abstract:

To effectively address the issue of ground vibration induced by the rail transit, a locally resonant metamaterial surface wave barrier (LRMB) vibration isolation method was developed based on the concept of acoustic metamaterials, and the structure model was constructed using concrete and rubber pad. According to the theory of elastic dynamics in semi-infinite space, an analytical calculation formula for LRMB bandgap was derived, and the influences of rubber pad and concrete on LRMB bandgap characteristics was analyzed. The vibration isolation performance of LRMB was further analyzed based on the measured ground vibration induced by the rail transit. The results show that the generation of LRMB surface band gap is mainly related to its vertical vibration, and the band gap calculation method for LRMB assuming vertical vibration mode is accurate. Increasing the thickness of the rubber pads decreases the starting frequency of the bandgap and increases its width. Conversely, increasing the width of the rubber pads increases the starting frequency of the bandgap and decreases its width. Additionally, increasing the mass of the concrete decreases the starting frequency of the LRMB bandgap and increases its width. The vibration isolation efficiency can be improved by increasing the number of primitive cells and the vibration isolation coefficient with 4−6 cells reach 20−25 dB. Using Jinan Rail Transit Line 1 project as an example, the ground vibration attenuation can reach 70%−80% after using LRMB, validating its strong vibration isolation performance.

Key words: acoustic metamaterial, surface wave, wave barrier, band gap characteristics, vibration isolation performance