The Effects of Voids on the Dynamic Response of Tunnels Under Train Induced Vibration Loads

This paper presents results of the voids influences on the dynamic response of tunnel linings and surrounding strata acquired in series of model tests. An experimental model of a tunnel was tested with a void of varying size (ratio of void width to tunnel diameter of 0.13, 0.27, and 0.4) and location (at tunnel apex, haunch and invert). During the tests, the tunnel invert were applied with three types of vibration loads: a sinusoidal load with a fixed frequency, a sinusoidal sweep load, and a simulated train load. The tunnel lining and soil response were recorded by accelerometers, with analysis results presented in both time and frequency domain. The experimental results manifest that the voids can have a distinct influence on the tunnel and soil dynamic response, with a clear amplification of tunnel and soil response for certain cases. The test results also demonstrate that the tunnel and soil response are sensitive to the void size and location in the near field. However, with increased distance from the excitation source, the void effects on the tunnel and soil dynamic response gradually declines.