Dynamic responses of bridge-approach embankment transition section of high-speed rail

Based on the vehicle-track coupling dynamics theory, a new spatial dynamic numerical model of vehicle-track-subgrade coupling system was established considering the interaction among different structural layers in the subgrade system. The dynamic responses of the coupled system were analyzed when the speed of train was 350 km/h and the transition was filled with graded broken stones mixed with 5% cement. The results indicate that the setting form of bridge-approach embankment section has little effect on the dynamic responses, thus designers can choose it on account of the practical circumstances. Because the location about 5 m from the bridge abutment has the greatest deformation, the stiffness within 0–5 m zone behind the abutment should be specially designed. The results of the study from vehicle-track dynamics show that the maximum allowable track deflection angle should be 0.09% and the coefficient of subgrade reaction (K30) is greater than 190 MPa within the 0–5 m zone behind the abutment and greater than 150 MPa in other zones.