Novel phononic-like crystal pile structure with low-frequency and multi-frequency band gaps for vibration isolation

The environmental vibration caused by rail transit operation, especially low-frequency rail transit vibration, can have harmful effects on adjacent buildings and human health, and it has the characteristics of long transmission distance, difficult isolation, and high harm. In response to the low-frequency vibration hazards caused by rail transit, this paper adopts a periodic pile vibration isolation method and proposes a phononic-like crystal (PLC) pile structure composed of pipe pile, PLC metaconcrete material, and matrix. Firstly, the band structure of the PLC pile structure is calculated using the finite element method, and its attenuation characteristics on vibration waves are analyzed. Secondly, the influence of parameters of the PLC pile structure on its band gap (BG) is analyzed, and its vibration isolation BG is regulated, providing guidance for the application and design of the PLC pile structures in different practical engineering projects. Finally, the vibration isolation performance of the PLC pile structure in practical engineering applications is analyzed and verified using on-site measured vibration data. The results indicate that the PLC pile structure opens five low-frequency BGs in the frequency range of 200 Hz, and the attenuation amplitude of vibration is mostly above 15 dB. Moreover, the field vibration monitoring data show that the PLC pile structure can significantly attenuate the propagation of vibration in the soil, and the maximum vibration acceleration amplitude is reduced by 43.9%, which has remarkable vibration isolation effect. The PLC pile structure proposed in this paper has significant vibration isolation effect, which can provide novel method and technology for solving low-frequency vibration problems caused by rail transit operation, and also provide reference and guidance for designing periodic pile structures for vibration isolation.