Identification of Source Time Function for Train-induced Vibration of Underground Tunnels

The objective of this paper is to identify the dynamic source time function for the train-induced vibration of underground tunnels. Under the consideration of the gaps between adjacent slabs and the constraint from equal-spacing fasteners, the vertical force loaded by the moving train is modelled by a periodical source time function. Consequently, the induced vibration at any specified observation point on the inner wall of the embedded waveguide can be determined on the basis of the transition matrix (T-matrix) method. On the other hand, thanks to the Taipei Rapid Transit Corporation for the permission of an in-situ test, the train-induced vibration on the inner wall of underground tunnels was measured to validate the proposed periodical source time function and further, to identify the associated loading parameters. It can be found that the vibration responses determined numerically by the identified model, both the waveform in time domain and the Fourier spectrum in frequency domain, are in good agreement with the measured signals.