Study On Operation Mechanism And Technology Of Large-scale Maintenance Machine Used In High-speed Railway Ballast Bed

Ballast bed undergoes degradation, deformation and other diseases owing to the dynamic load of high-speed train, resulting in changes of track geometries, reduce of track stability, or even threatening traffic safety. By using large-scale tamping machine and dynamic stability machine, the geometries and elasticity of track can be improved, the resistance and stability of ballast bed can be enhanced. Therefore, the use of large-scale tamping machine and dynamic stability machine is inevitable for protecting the high geometric regularity and high stability of high-speed railway ballasted track. However, the shortage of systematic study on mechanical behaviors of high-speed railway ballast under tamping and dynamic stabilizing makes it unable to scientifically guide the operation of large-scale maintenance machines.Based on the analysis of previous researches, tamping facility/high-speed railway ballast bed coupling model and dynamic stabilization facility/high-speed railway ballast coupling model are established using discrete element method in this thesis. Then, the mechanical behaviors of high-speed railway ballast bed under tamping, dynamic stabilizing and dynamic train load are studied from the microscopic view, the effects of tamping parameters and dynamic stabilizing parameters on mechanical behaviors of high-speed railway ballast bed are analyzed. Finally, rational technological parameters of tamping and dynamic stabilizing are proposed in this thesis, and the operation processes of large-scale maintenance machines are optimized. The major works and conclusions are as follows:(1)Large-scale maintenance machine tamping facility/high-speed railway ballast bed coupling model, large-scale maintenance machine dynamic stabilization facility/high-speed railway ballast bed coupling model and train load/high-speed railway ballast bed coupling model are established using discrete element method.Ballast particles are simulated by particle clusters of different sizes, and realistic shape tamping tines are established by bonding balls together through self-compiled program in PFC3D software. Motion characteristics and vibration characteristics of tamping facility and dynamic stabilization facility are simulated according to their working principles. Train load is simulated based on field test data of sleeper pressure under dynamic train load.(2)The mechanical behaviors of high-speed railway ballast bed under tamping are studied, the effects of tamping parameters on mechanical behaviors of high-speed railway ballast bed are systematically analyzed, and rational technological parameters of large-scale tamping machine are proposed.The motion characteristics of ballast, compactness change of ballast bed, contact relationship between ballast particles during tamping operation are studied from the microscopic view, then the effects of tamping parameters, such as penetration velocity, vibration frequency, penetration depth, vibration amplitude and squeezing time, on tamping quality are analyzed, and the technological parameters of large-scale tamping machine are optimized.(3)The mechanical behaviors of high-speed railway ballast bed under dynamic stabilizing are studied. The influences of dynamic stabilizing parameters on mechanical behaviors of high-speed railway ballast bed are systematically analyzed, and rational technological parameters of large-scale dynamic stabilizing machine are proposed.The effects of dynamic stabilizing on ballast settlement, ballast stress and ballast vibration accelerations are studied, then the influences of dynamic stabilizing parameters, such as vertical force, horizontal vibration amplitude and horizontal vibration frequency on mechanical behaviors of high-speed railway ballast bed are analyzed, and rational technological parameters of large-scale dynamic stabilizing machine are proposed.(4)The mechanical behaviors of high-speed railway ballast bed under different operation sequences of large-scale maintenance machines are studied, and the operation processes of large-scale maintenance machines are optimized.The influences of the different operation sequences between large-scale tamping machine and large-scale dynamic stabilizing machine, large-scale dynamic stabilizing machine and train load on ballast settlement, ballast contact state and ballast vibration accelerations are analyzed, finally the reasonable operation sequences of them are proposed.