Analysis of Critical Speed of Track-Subgrade-Groundwork System of Passenger Dedicated Line

In view of actual situation of passenger dedicated line in China,a vibration model of the coupling system of track-subgrade-groundwork under the action of moving load was established,and the critical speed of the track-subgrade-groundwork system was analyzed under the conditions of ballasted track and ballastless track respectively on the embankment.Further on,the influences of deformation modulus and thickness of subgrade bed on the critical speed were discussed.The results show that there is a critical velocity in the track-subgrade-groundwork system under the action of a single moving load,and this critical velocity can be called the critical speed of railway line.Moreover,this critical speed of railway line is mainly dominated by the factors:the flexural rigidity of the track,the vibration mass of the track-subgrade,and the elastic modulus of ground soil.To increase the critical speed of railway line,there are some useful measures as follows:increasing the bending stiffness of track,improving and strengthening the soft ground,and selecting the light subgrade filling material to reduce the vibration mass of subgrade.