Analysis Of Structure Mechanics And Wheel/Rail Dynamic Interaction Of Ballastless Track In High-Speed Railway

Ballastless track is a new kind of track which uses concrete or asphalt track bed instead of ballast bed. It has the remarkable characteristics of low maintenance, high stability, high smoothness and good durability. Railway line maintenance is reduced and its utilization rate is improved by using ballastless track. The safety and speed of train negotiation are both improved. Ballast is a kind of non-renewable resources. Ballastless track is beneficial to environmental protection because the use of ballast is reduced. Ballastless track is more economic than ballast track in long run. High-speed railway is energetically developed in many countries at present. More and more new technology is used to build high-speed railway. Ballastless track is a new important choice of high-speed railway track structure. To alleviate the contradiction between the fast growth of the national economic and shortage of the railway transport capacity, the speed passenger dedicated line in Chinese railway is fast developed. The structure mechanical conditions of ballastless track are closely related to the safety of track structure, and the dynamic performances of ballastless track have influence on vehicle running safety and ride comfort. Therefore studies on the structure mechanics and wheel/rail dynamic interaction of ballastless track are very important from the practical and cognitive points of view.The history and the studies of the structure and mechanics of ballastless track in the past and now in the world are reviewed. On the basis of track structural mechanics and vehicle-track coupled dynamics theory, the structure mechanics and wheel/rail dynamic interaction problem of ballastless track are solved with finite element method. The analysis objects of ballastless track are the slab track and the twin-block ballastless track because these two kinds of ballastless track are found well application in China. The vehicle parameters are come from CRH2 and CRH3 which were independently developed in China.The main research work in the present dissertation involves:Three-dimensional finite element models of slab track and twin-block ballastless track are established. Mechanics characteristics under design load of ballastless track are studied, including the influence of the track structure form and parameters, key parameters of subgrade. A vehicle-ballastless track dynamic model is established on the basis of vehicle-track coupled dynamics theory. In this model, multi-body system (MBS) modelling techniques are combined with the techniques based on the finite-element method (FEM). MBS modelling is used for modelling the vehicle and FEM for simulating the ballastless track. Dynamic responses of ballastless track are simulated with German railway spectrum of low irregularity as the irregularities of rail. The simulation results are compared with the experiment results measured on comprehensive experimental section of ballastless track on Sui-Yu Railway Line. The numerical results are in good agreement with the test ones, and the dependability of the vehicle-ballastless track dynamic model is verified at the same time.The established vehicle-ballastless track dynamic model is used to analyze the dynamic response of slab track caused by impulse, harmonic and random track irregularity. The influence of the flat length, the height of high weld and dipped weld composed by difference long or short wavelength are analyzed. The rationality about the limited value of wheel flat and weld in Railway Technical and Managemental Regulations is verified. Vibration characteristics of ballastless track of the high speed passenger dedicated railway line under excitations from the stochastical track irregularities are analysed. While the vehicle velocity is in the range 200～350km/h, the influence of velocity on the dynamic responses of slab track and twin-block ballastless track is studied.At last, the influence of the ballastless track structure parameters on dynamic performance is studied. These structure parameters include the stiffness and damping of rail pad, resilient modulus of the surface layer of subgrade, elastic modulus of cement asphalt mortar of slab track and the bed slab thickness of the twin-block ballastless track.