Influence of Heavy Axles on the Dynamic Response of the Existing Railway Ballast Track under Freight Vehicle Running

In order to relief railway transportation pressure in China, the load-raising reform of existing railway lines is paid much more attention. In load-raising reform of existing railway lines process, the most obvious improvement is the increase of vehicle axle load. Using the theory of wheel-track dynamics, The vertical dynamic model for the ballast rail track and heavy haul train interaction could be built. In this model, the heavy haul train is regarded as a subsystem with 10 degrees of freedom, and the ballast track structure is built using finite element method. The two subsystems are coupled using via non-linear Hertz contact mechanism considering the influence caused by track irregularity. This paper analyzes the dynamic response between train and track using the combination method of new rapid explicit integration method and Newmark integration method. And the dynamic response of existing ballast track under heavy haul train of different loads which are 25 t, 27 t and 30 t is specialized analyzed. During the analysis process, the dynamic performance indexes include: rate of wheel load reduction, wheel-rail vertical force, dynamic displacement of the ballast track, vibration acceleration of ballast track, and dynamic stress distribution of ballast track. The research results show that: 1). When heavy haul train are running on ballast track, every dynamic performance index is still within the national standards, and it can meet the dynamic requirement for running heavy haul train. 2). The trends of the dynamic displacement of the track structure under different loads are similar to one another. And the dynamic displacements of the rail under 27 t-axle-load and 30 t-axle-load increase 16% and 22% respectively, compared with the 25 t-axle-load. 3). In general it can be concluded that the growth proportion of the dynamic stress of the track structure is similar to the dynamic displacement. And the dynamic stresses of the rail under 27 t-axle-load and 30 t-axle-load increase 15% and 22% respectively, compared with the 25 t-axle-load.