Study on the Dynamic Response of the Track/Subgrade under Moving Load

Based on the theory of layered beam and viscoelastic semi-infinite solid,a coupled dynamic analysis model of track/subgrade is developed.By means of moving coordinate and Fourier Transform,the steady state dynamic response of the track/subgrade system under moving harmonic point load is obtained in the wavenumber domain.The rail,sleeper displacement and the interaction force between ballast and subgrade in space domain are obtained by using the Fast Fourier Transform.Numerical examples are provided to examine the influence of load velocity on the subgrade displacement.Results show that the peak amplitudes of subgrade vertical displacement increase with the load velocity.In low-speed scope,the load velocity has slight effect on subgrade displacement.When the load velocity is close to the Rayleigh wave speed of the subgrade,the maximum subgrade displacements have a significant increase.The vertical displacement distribution of the subgrade exhibits apparent oscillations and the wavelength decreases as the load velocity increases.