Study On Dynamic Responses Of Irregularity Ballastless Track For High-Speed Railway

Slab ballastless track is being widely used due to good longitudinal and lateral stability, safe operation and comfortable circumstance for passengers. As train speed increases, dynamic responses of track and ground along the railway line become more substantial under rail irregularity (e.g. wheel-rail contact irregularity, subgrade settlement), affecting the travel condition and train safety, and inducing the environmental vibration. The train-track-subgrade dynamics is an important subject, concerning high-speed railway plan, design and maintenance.The main contents and conclusion of this thesis include:1. A vehicle-track-subgrade coupling system in longitudinal direction is established, and the effect of vehicle-track response under the irregularity is analyzed with this model, indicating the necessity of establishing high-speed railway track irregularity spectrum for China’s high-speed railway lines. Through parametric study, the recommended values of fastener’s stiffness and spacing of China high-speed railway are proved to be reliable, the subgrade distribution stiffness recommend range is3×108N/m2～6×108N/m2.2. A typical subgrade settlement patterns assumption in introduced here. We get the subgrade settlement control standards to meet the requirement of passenger comfort and safety of train operation. The settlement standard of China’s high-speed railway (20m/15mm) is conservative and safe.3. Considering the vibration spread of track and subgrade media is non-uniform in cross section and uniform in the longitudinal direction, the author build a2.5dimensional finite element model for track-roadbed-ground system. based on this model, the "Mach effect" when the speed of load source close to or exceed critical speed of surface soil is analyzed, demonstrating the phenomenon that vibration wide spread in ground. When the load source is a vibration load source, even the speed of load is below the critical velocity of layered ground, the ground may also have corresponding resonance frequency.4. The dynamic experimental equipment for slab track high-speed railway is present, which can be used to carry out test on interaction of track structure-subgrade system. Results show that the1st order natural frequency of the subgrade system is16Hz approximately. With the water level rises, the first-order mode frequency decreases and the static and dynamic stiffness of subgrade are weakened significantly which affect the vibration characteristics of the track structure and deformation characteristics. An engineering attempt with injection of polymer material between the roadbed surface and the concrete base of the slab track is adopted to uplift the track structure uniformly.5. Based on Hertz contact model, a3D finite element model for vehicle-track-subgrade is built, realizing the responses analysis of complexity slab track and subgrade structure under moving train loads. This model focuses on the dynamic responses of track and subgrade under different speeds and track irregularity spectrum, the results indicate that the strain on frame track slab surface increase about35%-40%compare with plain track slab, and vibration levels on ground caused by embedded rail track decrease3dB-5dB compare with plain track slab case.In this paper, theoretical analysis, model test and numerical simulations are performed to explore the dynamic characteristic and mechanism of vehicle-track-subgrade system, and achieve innovation on track irregularity spectrum; the subgrade settlement standards, the critical speed of subgrade system, and the track slab optimization, etc.