Dynamic response propagation in urban subway tunnels: an indoor large-scale simulation of crack-induced vibrations

Abstract Urban subway systems commonly experience various internal issues, primarily cracks. These flaws become more pronounced under the dynamic response elicited by train-induced vibrations. Drawing from existing theoretical research, an indoor large-scale model was designed and a model box was constructed, utilizing nylon to simulate the tunnel segment. The simulation method included grooving and cutting to simulate the real-world scenario, alongside the implementation of sinusoidal load and frequency sweeping excitation load to study the propagation laws of dynamic response within and around the tunnel when cracks existed. Findings revealed that voltage, excitation force, and acceleration responses are linearly related, with the dynamic response at each measurement point exhibiting varying degrees of attenuation as the propagation distance increases. This attenuation is markedly noticeable at the interface where the material changes. In time and frequency domains, the fully cracked section demonstrates higher vibration levels and increased acceleration amplitudes compared to an intact section. The measurement point’s expansion effect within the tunnel considerably outweighs that of the surrounding soil. Cracks influence mainly by reducing material integrity and connectivity, consequently lowering the vibration response threshold while intensifying local self-oscillation characteristics.