Study On Vibration Of Train-Track-subgrade Coupled System And Running Safety Of Train In Earthquake

The subgrade is a weak and unstable part in the railway engineering. For a long time, the dynamic subsidence deformation and service security of subgrade under the train operating conditions have been a problem widely concerned in engineering. With the great development of high-speed railway, the issues of the wheel-rail dynamic interaction, the running safety and comfort of train, the service reliability of track and subgrade are more outstanding, however these problems still lack enough research in China. Therefore, the interaction between the trains, track and subgrade has become one urgent mechanical problem which needs to be carried out in the high-speed railway engineering.Additionally, China is a country seriously affected by earthquake disasters with high-frequency seismic activity, intensity, light source and widely distributed. With the large-scale construction of high-speed railway and many of which through multiple seismic zone, seismic waves may threat running safety passing through the track structure when earthquake occurs. Therefore, the running safety issues in earthquake is also an urgent research topic.According to the problems of train-track-subgrade coupled vibration and running safety of train in earthquakes which are mentioned above, the research is carried out as follow:1. A brief review is given with regard to the studies on train-track-subgrade dynamic interaction and running safety in earthquakes at home and abroad, and some details which are worth learning and problems which still need to be studied are also pointed out.2. A four-axle rolling stock dynamic model is set up and the dynamic motion of each part is given with reference to relevant literature. The dynamic model and equation of ballast track, discontinuous slab track, framed slab track, continuous slab track, bi-block ballastless track, floating slab track and ladder-shaped track are established.3. Three dimensional spatial dynamic model of subgrade is set up, by using the dynamic substructure method. In the model, subgrade is broken up into various substructure according to the structure characteristics, and then3D viscoelastic partial differential dynamic equation of each substructure is discretized by utilizing galerkin method. The ordinary differential equations about the generalized modal coordinates of the overall structure are obtained by assembling the equation of each substructure through satisfying the compatible displacement conditions.4. The principle of wheel-rail interaction and track-subgrade interaction, numerical solution methods for train-track-subgrade coupled vibration and train-track-subgrade dynamics simulation software TTSDYNA are introduced. A more detailed presentation is given about wheel-rail interaction, including the definition of wheel-rail contact coordinate system and the coordinate transform, the static/dynamic single point and two point wheel-rail contact geometric relationships, and the calculation method of wheel-rail normal force and creep force.5. Without considering the vibration of subgrade, the vehicle-track coupled dynamic model is validated by the commercial software. The coupled dynamic model based on dynamic single-point wheel-rail contact is validated by the SIMPACK software, while the coupled dynamic model based on dynamic two-point wheel-rail contact is validated by the ADAMS/Rail software.6. The vibration performance of train-ballast track-subgrade coupled system and train-ballastless track-subgrade coupled system are studied, and the analytical method for that two systems is reliable by comparing the calculation results with the test results in Qinhuangdao-Shenyang passenger railway line and Beijing-Tianjing intercity railway line respectively.7. The influence of the structure parameters of ballast track, ballastless track and subgrade on dynamic response of train-track-subgrade coupled system are analyzed and contrasted.8. To take continuous slab track as an example, a train-track-subgrade coupled dynamic model during earthquake is set up. Three commonly used seismic input method such as the directed solving method, the pseudo-static displacement method and the large mass method are introduced. Which method is suitable for train-track-subgrade coupled system that contains nonlinear wheel-rail contact relation is discussed. And then dynamic response of train-track-subgrade coupled system during earthquakes is studied based on the directed solving method. Compared with the calculation of the relevant literature, the correctness and reliability of the direct solving method is verified. Furthermore, the seismic response is analyzed based on the large mass method and compared with the result using the directed solving method under the same calculation parameters. Finally, the influence of the track irregularity in model is analyzed.9. The running safety of train in earthquakes is studied. Firstly, a typical seismic wave are selected in the analysis and normalization method are introduced. Secondly, the influence law of earthquake intensity and train speed is analyzed and the running safety domain for the train during the earthquake is obtained, by using the train-track-subgrade coupled dynamic model during earthquake which has been verified. Thirdly, the seismic response is analyzed when the train passing over the curved track. Finally, the main derailment form during earthquake is summarized and a simulation example of two point contact and derailment in earthquake is given.10. The principle of the single-degree-of-freedom isolation system is described, and then three kinds of seismic isolated track with different slab length are proposed by learning from lateral isolation ideas of isolated building structures in Japan and referring to floating slab track which has the good vertical vibration isolation in the actual works. Vibration transmission rate of different track structure is studied and the influence law of lateral stiffness of the isolator and the slab length on vibration transmission rate for isolated track is analyzed, using the simplified vehicle-track coupled model. Based on the integrated train-track-subgrade coupled dynamic model during earthquake, seismic response of different track structure are contrasted and analyzed. Finally, the influence law of lateral stiffness of the isolator and the length of the slab on seismic response of isolated track is analyzed and the structural parameters of isolated track is recommended.