Effect of Degraded Subgrade Stiffness on Rail Geometry and Train Vibration in High-Speed Railways

The degradation of railway subgrade stiffness will cause the acceleration of track degradation and deteriorate ride comfort and safety. It is hard to foresee these problems because both track substructure and subgrade are not visible to inspect. To study the influence of subgrade stiffness degradation on high-speed train and track system, 3D FEM analyses of the Fuxing trains and ballastless tracks were conducted to simulate different degradation conditions of roadbed stiffness. Firstly, the numerical model was verified by the field measurement of vibration velocity at the concrete base in the Beijing–Tianjin high-speed railway. Then, the influences of the degradation of roadbed stiffness on the rail displacements and train dynamics were analyzed. It is found that since the ballastless track had quite high rigidity, the uneven degradation of roadbed stiffness did not result in obvious additional increase of rail displacement. However, the uneven degradation of roadbed stiffness resulted in larger vibrations of train wheels. Particularly, the wheel accelerations were more sensitive to the uneven degradation of roadbed modulus amplitudes than the wavelengths.