Response of railway track coupled with a stratified ground consisting of saturated interlayer to high-speed moving train load

A three-dimensional track-ground model is developed to study vibrations induced by high-speed train. The train loads are simplified as a series of moving point loads. The track system consists of rail, pads, sleeper and ballast. The ground consists of a treated soil layer, a crust, a saturated layer and semi-infinite bedrock, which considers the alternate distribution of viscoelastic and poroviscoelastic media. The ground is coupled with the track system according to the continuity conditions between the ballast and ground surface. Fourier transform is applied to solve the governing equations. Some adaptions are made on the basis of classical stiffness matrix method to give solution to the stratified ground. Semi-analytical solution to the coupling system is derived in the wavenumber domain. Solution in spatial and time domains is obtained with the aid of inverse fast Fourier transform (iFFT). The present method is verified against the published analysis results first. Dynamic responses of the coupling system such as displacement, acceleration and pore-water pressure, are then comprehensively investigated. The results indicate that the existence of ground water significantly influences the surface displacement of the ground while the influence on velocity and acceleration is weaker; 'critical speeds' for vertical displacement and acceleration exist for ground but the variations with distance from track center are complicated and depend on soil properties; load speed greatly influences pore-water pressure distribution while the influence of drainage condition is relatively small.