Dynamic responses of existing-railway subgrade with train speed increasing

Considering the increase of speed-trains in existing railways of China, i.e., passenger train will run at speed of 200 km/h and heavy truck at speed of 120 km/h, thus the dynamic responses of railway subgrade with train speed increasing are studied. Firstly, the coupled dynamic model of train-track-subgrade is applied to calculate the interaction force between wheel and track. Subsequently, according to nonlinear numerical analysis, the dynamic responses of subgrade are analyzed with different train groupages and running speeds, including the dynamic subgrade stress, displacement and acceleration, and their distribution and attenuation in subgrade. Moreover, relationships between the design parameters of subgrade and its dynamic responses are also studied. Field measured data were used to verify the numerical results. It is found that the influence of train speed on subgrade dynamic responses is limited, whereas the axial load of train affects subgrade greatly; there is an optimum stiffness for strengthened subgrade(i.e. 120 MPa). With the thickness of ballast increasing, the subgrade dynamic stress reduces linearly, but dynamic displacement and acceleration have a negligible change.