Effects and Control Mechanisms of Isolation Barriers on Metro Train-Induced Building Vibrations

Metro train-induced environmental vibrations may adversely affect the performance and comfort of buildings near metro lines, making it necessary to select suitable isolation barrier materials for vibration control. To evaluate the vibration isolation performance of different barrier materials, a vehicle–track coupled dynamic model and a three-dimensional tunnel-soil-structure finite element model were established to predict vibration sources and structural responses. Based on wave propagation characteristics and impedance theory, an impedance-based material selection approach for isolation barriers was proposed. Concrete and foam were selected as representative high- and low-impedance materials, respectively, and were compared with open trenches to evaluate their isolation performance and control mechanisms. Results indicate that building vibrations are mainly concentrated within 20–80 Hz, with dominant peaks around 40–50 Hz. Open trenches provide the most effective low-frequency attenuation, foam-filled trenches achieve stable broadband isolation, and concrete walls are mainly effective at mid-to-high frequencies. Low-impedance filled trenches offer a favorable balance between vibration reduction and engineering feasibility. The findings provide a reference for the design and selection of isolation barriers for buildings adjacent to underground metro tunnels.