Abstract: Based on the theory of phononic crystal, a periodically arranged horizontal tube vibration isolation method is proposed, and its vibration isolation performance for subway is discussed. By combining the plane wave expansion method with Bloch theorem, the band structure of the horizontal tube is obtained. A three-dimensional ABAQUS refined model of track-tunnel-soil interaction is established to further verify the damping effect of periodic horizontal pipe on subway vibration. In addition, the influence of horizontal tube material and its related parameters on the vibration isolation band gap is explored. Some laws are revealed. The attenuation region obtained by numerical calculation is consistent with the band gap results of theoretical analysis, and the vibration isolation effect of periodically arranged horizontal tubes on a specific frequency band is significant with a wider vibration isolation frequency band. The attenuation region gradually moves downward with the decrease of elastic modulus. The initial value of vibration isolation frequency band increases with the increase of pile diameter. Additionally, as the axial spacing increases, the upper and lower limits of the attenuation region simultaneously decrease, which also reduces the band gap width of the whole vibration isolation structure. The calculation shows that the frequency band range of periodic horizontal tube under different parameters is within 40?900 Hz.

Key words: subway vibration isolation, phononic crystal theory, plane wave expansion method, attenuation domain, band gap