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Abstract The underground railway coupling analysis model was established and used to study the dynamic response of track systems and saturated soil. The model was divided into four parts，the moving train，floating-slab tracks，liner and saturated ground. The train load was simulated by a series of moving constant or harmonic load in accordance with the geometry of a real train. The tracks consisted of an upper Euler-Bernoulli beam to account for the rails and a lower Euler-Bernoulli beam to account for the slab. By adopting the method of 2.5D FEM，the elastic theory and the Biot’s theory were used to simulate the liner and saturated porous medium respectively. The floating-slab tracks and soil medium were coupled by the boundary conditions at the tunnel invert. The three-dimensional time-space domain dynamic response was obtained from the fast inverse Fourier transform (IFFT). Computed results show that with increasing train velocity and self-vibration frequency of the moving harmonic load，the dynamic responses of the ground surface increase obviously. The maximum ground surface responses generated by the moving constant load are located directly over the tunnel centerline with a constant space attenuation rate. The dynamic responses of ground surface induced by moving harmonic load are larger than those induced by moving constant load and become the strongest at certain distances from the tunnel centerline. The distribution of velocity spectrum for the rail and ground surface is centered on self-vibration frequency of the harmonic load.
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2015, Vol. 34 
