Field Application of Polyurethane Foam in-Filled Pile Barrier in Mitigating Metro Train-Induced Building Vibrations

Building vibrations induced by metro trains may affect adjacent structures and cause discomfort in residences. To mitigate these adverse effects, this paper proposes a vibration mitigation countermeasure called the polyurethane foam in-filled pile barrier (PFIPB), in which a row of piles filled with polyurethane foam form a wave barrier in the propagation path. The field application of the PFIPB is described in detail. A series of in-situ tests was conducted to evaluate the mitigation performance of the PFIPB. The experimental results demonstrate that the PFIPB at the test site can reduce the peak accelerations of metro train-induced building vibrations by up to 66.3%, and achieves a maximum average insertion loss of 14.8[Formula: see text]dB. After validating a corresponding finite element model, a comprehensive vibration evaluation of the test-site building is conducted. A parametric study is conducted to investigate the effects of key pile barrier parameters (e.g. length, spacing, diameter). The results show that the PFIPB efficiency generally improves with increasing pile length and decreasing pile spacing, whereas increasing pile diameter provides negligible improvement for vibrations at 20[Formula: see text]Hz. Both the in-situ tests and numerical analysis confirm the significant effectiveness of the PFIPB in mitigating metro train-induced building vibrations.