Rail movement and ground waves caused by highspeed trains approaching track-soil critical velocities

The increased speeds of modern trains are normally accompanied with increas ed transient movements of the rail and ground, which are especially high wh en train speeds approach some critical wave velocities in the track-ground system. These transient movements may cause large rail deflections, as well as structural vibrations and associated noise in nearby buildings. There a re two main critical wave velocities in the track-ground system: the veloci ty of the Rayleigh surface wave in the ground and the minimum phase velocit y of bending waves propagating in the track supported by ballast, the latte r velocity being referred to as the track critical velocity. Both these vel ocities can be exceeded by modern high-speed trains, especially in the case of very soft soil where both critical velocities become very low. The disc ussion in this paper focuses on the effects of transient rail deflections o n associated ground vibrations in the cases of train speeds approaching and exceeding Rayleigh wave and track critical velocities. The obtained theore tical results are illustrated by numerical calculations for TGV and Eurosta r high-speed trains travelling along typical tracks built on soft soil.