Impact of speed raising on dynamic response of bridge-subgrade transition of existing railway

Based on the infinite artificial boundaries,three-dimensional finite element model of existing railway subgrade of bridge-subgrade transition is established to study the response properties of the subgrade under moving load produced by trains of raising speed from 80 km/h to 160 km/h,considering the structure feature of inverse echelon.Moving load produced by trains passing through bridge-subgrade transition is simulated by a series of moving dynamic surface forces on subgrade surface due to wheel loads.It is pointed out that the peak value of dynamic stress on subgrade surface will increase by 20 percent when the train speed is upgraded to 160 km/h from 80 km/h,and vertical dynamic stress on the subgrade surface declines with depth in the form of exponential decay.Compared to the general subgrade,the brigde-subgrade transition produces greater dynamic stress on the conditions of the speedup of trains.