The vibrations of vehicle-track-saturated ground coupling system subjected to moving train loads are investigated by a semi-analytical approach. The theoretical model is divided into three components: the vehicle is described as a multi-rigid-body system

and a linear Hertizian contact spring between each wheel and the rail is used to simulate the dynamic wheel-rail interaction forces; a periodically supported Euler beam is introduced to simulate the track system; a fully saturated poroelastic half-space is used to simulate the ground and governed by Biot’s theory. Train loads include two parts: the axle loads and the dynamic wheel-rail loads assumed to be generated from the track irregularity. The governing equations of each component are solved by using Fourier transform

and these components of the whole system are integrated to meet the displacement compatibility and force equilibrium by the substructure method. The time domain responses of the ground are obtained through the fast Fourier transform. On the basis of the analysis of the dynamic wheel-rail loads

the dynamic responses of the ground subjected to the axle loads and the dynamic wheel-rail loads are investigated. Influences of the sleeper span and the soil intrinsic permeability on the soil dynamic responses are also analyzed. It is concluded that the dynamic wheel-rail load has important contribution to the far-field ground vibrations

and also the sleeper span has obvious influence on the track and ground vibrations.