Dynamic Response Modeling of High-Speed Railroad Ballastless Track Over Pile-Raft Foundation

Ballastless tracks have been extensively used in newly built high-speed railroads in China. Most of their foundations are constructed without pile improvement; however, the pile-raft design concept has been increasingly used as a rapid yet effective construction technique to reinforce the foundations. Limited attention has been paid to the behavior of this foundation system under dynamic loads either in the laboratory trials or field applications. This study presented the results of displacement responses obtained from three-dimensional (3D) dynamic finite element simulations of a typical high-speed railroad ballastless track over the pile-raft foundation. Both the soft ground improved by the pile-raft technique and the unreinforced ground, as control, were modeled and compared to quantify the effectiveness of the ground improvement in mitigating the detrimental effects of dynamic impact loads induced by high-speed trains. Other features of the 3D finite element models included the simulation of the moving train at different speed levels, the use of nonlinear constitutive models for track foundation geomaterials, and the consideration of the pile-soil interaction. The results of this study could lead to further research in this area as guidelines to design piled raft foundations economically.