Dynamic subsoil responses of a stiff concrete slab track subjected to various train speeds: A critical velocity perspective

The advent of new high-speed trains with increased operation speed has made the slab track structure a viable alternative to the traditional ballast track. However, the high rigidity of the stiff slab layers that replaces the ballast material make the dynamic responses of concrete slab tracks very different to those generally expected in ballast tracks. Inclusion of stiff layers between the rail and subsoil in a concrete slab track obscures understanding of dynamic subsoil responses with respect to theoretical critical velocity. In this study, we systemically investigated the dynamic responses of the concrete slab track to various train speeds and subsoil stiffnesses. A complete finite element model including the vehicle, rail, track, and subsoil in two dimensions was developed. Numerical results revealed that the degree of retardation of the elastic strain energy related to the critical velocity for the subsoil dominated the delayed arrival of the peak vertical displacement, thereby expanding the hysteretic loop of the stress paths, resulting in erratic distribution of the elastic strain energy in the subsoil.