Research On Vibration Theory And Application Of High-speed Railway Ballasted Track

On most passenger dedicated railway and existing speed-increasing railway lines with the operation speed of 250 km/h in China, the ballasted track is applied. Under the condition of high-speed operation, many problems arise, such as serious track irregularity, large structural dynamic response, uneven stiffness transition, multiple track maintenance and repair. Therefore, attention should be paid to ballasted track vibration performance in operation. The ballasted track irregularity is directly related to the rail service status. To solve the random vibration problems for the ballasted track is one of the difficult problems in the field of railway at present. The comprehensive and systematic research has been done for the ballasted track in terms of the random vibration theory and its application including the track irregularity characteristics, mechanical model, reasonable transition, calculation methods, etc. It provides a theoretical basis for the operation and maintenance of ballasted track. The main outcomes of this dissertation are listed as follows.(1) In consideration of the ballasted track irregularity characteristics, the paper analyzed the sensitive track irregularity and its influence on the existing speed-increasing railway lines. The irregularity power spectrum for the ballasted track on the main railway lines in China was proposed and analyzed in detail.(2) With the details of vehicle and track taken into account, based on the vehicle-track dynamics theory, a coupling dynamic analytical model with full consideration of the track and its foundation was established. In the whole vehicle model, the primary suspension, secondary suspension, horizontal bumper, anti-hunting motion absorber as well as other components were considered. The solid element was used to simulate the track, while the link element was used to simulate the stiffness and damping characteristics of the fastener. In view of the complexity of the wheel-rail contact, the shape of the rail surface and wheel tread was discretized. The trace method was applied to dynamically determine the geometrical relationship of wheel-rail space contact.(3) Referring to the track irregularity power spectra at home and abroad, the power spectra of the pressure on the sleeper and the ballast bed acceleration for Vanguard motor train and CRH 2 motor vehicle were calculated. The paper studied the influence of the track irregularities on the dynamic response of different types of vehicle at the same vehicle operation speed and the influence of the track irregularities on the same vehicle at the different vehicle operation speed. Furthermore, the paper analyzed the mean squared error of the structural dynamic responses including the pressure on the sleeper and the ballast bed acceleration under the condition of track irregularities on the exiting railway in China and the effect law of irregularity wavelength and amplitude.(4) The dynamic responses of the vehicle-track system at different speed were calculated. And the influences of the speed-increasing passenger train, motor train and freight train on the dynamic responses of track structure were compared. By calculating the dynamic responses of the track structure under the condition of sleeper suspension, the paper analyzed the influence of sleeper suspension on the dynamic responses and maintenance of the track. By calculating the dynamic responses of the track structure when the ballast at the subgrade-bridge transition section was glued, the ballast glued scheme for the transition section was supposed to better satisfy the requirement on the track stiffness transition.(5) The ballast bed-sleeper space coupling model was built. By analyzing the change rule of the microscopic parameters, the mechanical behavior of the macroscopic ballast bed was explored. The contact force between particles would increase as the increase of loading frequency. The settlement of ballast bed mainly occurred in earlier stage of loading, and the settlement velocity obviously decreased in later stage of loading. The vibration acceleration of ballast bed would increase with the increase of loading frequency, and would decrease obviously with the increase of ballast bed depth. With the wider or heavier sleeper, the vibration acceleration of ballast bed would be smaller.(6) The space coupling analytical model for the type-Ⅲ sleeper in the ballasted track on the speed-increasing railway lines was established. The force distribution of each sleeper cross section was analyzed and compared under dynamic load. The force of sleeper directly relates to the pressure on the sleeper and the support from the ballast bed. The reason for sleeper injuries is a complicated problem related to the sleepers design, manufacturing, transportation, maintenance operations, operation conditions and so on.This paper established a relatively thorough random vibration theory, based on which the computational method is correct and the simulation results is credible. So this theory will have an important guiding significance for the operation and maintenance of the track.