An efficient 2.5D finite element numerical modeling approach was developed to simulate wave motions generated in ground by high-speed train passages. Fourier transform with respect to the coordinate in the track direction was applied to re-ducing the three-dimensional dynamic problem to a plane strain problem which has been solved in a section perpendicular to the track direction. In this study, the track structure and supporting ballast layer were simplified as a composite Euler beam resting on the ground surface, while the ground with complicated geometry and physical properties was modeled by 2.5D quadrilateral elements. Wave dissipation into the far field was dealt with the transmitting boundary constructed with fre-quency-dependent dashpots. Three-dimensional responses of track structure and ground were obtained from the wavenumber expansion in the track direction. The simulated wave motions in ground were interpreted for train moving loads traveling at speeds below or above the critical velocity of a specific track-ground system. It is found that, in the soft ground area, the high-speed train operations can enter the transonic range, which can lead to resonances of the track structure and the sup-porting ground. The strong vibration will endanger the safe operations of high-speed train and accelerate the deterioration of railway structure.
