Application and Vibration Reduction Properties of Prefabricated and Cast-in-Place Phononic-Like Crystal Polymer Concrete Track Bed in Subway Engineering

Subway plays an important role in building a three-dimensional urban transportation system and alleviating urban traffic congestion due to its advantages of land conservation, green environmental protection, safety and reliability, large transportation volume, and high efficiency. With the large-scale development of urban subway engineering and subway network, the vibration and noise problems generated during subway operation have become increasingly serious, especially low frequency vibration problems. First, this paper proposes a phononic-like crystal model based on local resonance theory, and based on this, a new type of vibration reduction material for phononic-like crystal polymer concrete has been developed. Second, the indoor test of phononic-like crystal polymer concrete is introduced, and trial mix tests are conducted on prefabricated and cast-in-place phononic-like crystal polymer concrete track bed. Finally, based on the indoor test and trial mix tests, prefabricated and cast-in-place phononic-like crystal polymer concrete track bed are designed for different subway engineering application environments, and applied to Nanjing metro line S6 and the north extension line of Nanjing metro line 1 in Nanjing of China for subway vibration control. The vertical vibration attenuation range of the prefabricated phononic-like crystal polymer concrete track bed is 1.25–125 Hz, and the lateral vibration attenuation range is 1.25–100 Hz, with maximum insertion losses of 12.2 dB for vertical vibration and 9.6 dB for lateral vibration, respectively. The vertical vibration attenuation range of the cast-in-place phononic-like crystal polymer concrete track bed is 2.5–250 Hz, and the lateral vibration attenuation range is 1.25–200 Hz, with maximum insertion losses of 11.82 dB and 6.98 dB for vertical and lateral vibrations, respectively. In the frequency range of 1–80 Hz, the maximum vertical Z-vibration level difference between the prefabricated and cast-in-place phononic-like crystal polymer concrete track bed and the ordinary concrete track bed of the tunnel wall is 5.662 dB and 5.057 dB, respectively. The results indicate that both prefabricated and cast-in-place phononic-like crystal polymer concrete track bed have good vibration reduction performance in subway operation, opening up low frequency vibration reduction band gap and achieving good low frequency vibration reduction effect. The phononic-like crystal polymer concrete track bed not only has good low frequency vibration reduction effect, but also has the advantages of low construction cost and good economy, so it has broad application prospects in subway engineering.