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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.

Societal interest on a faster transportation demands an increase of the train speed exceeding current operation speed of 350 km/h. To trace the pattern of variations in displacements and subsoil stresses in the concrete slab track system, finite element simulations were conducted. For a simple track-vehicle modeling, a mass-point system representing the moving train load was developed. Dynamic responses with various train speeds from 100 to 700 km/h were investigated. As train speeds increase the displacement at rail and subsoil increases nonlinearly, whereas significant dynamic amplification at the critical velocity has not been found. At low train speed, the velocity of elastic wave carrying elastic energy is faster than the train speed. At high train speed exceeding 400 km/h, however, the train speed is approximately identical to the elastic wave velocity. Nonlinearity in the stress history in subsoil is amplified with increasing train speeds, which may cause significant plastic strains in path-dependent subsoil materials.