Research On Mechanical Characteristics Of Sleepers And Track Beds Based On Discrete Element And Finite Element Coupling

Railway operation plays a vital role in Chinese population and resource circulation.After new railway construction and railway maintenance,the track bed is not yet suitable for high-speed railway operation,because the ballast particles are too loose,the density of the track bed is not high enough,and the mutual pinching force and friction between the ballast are weak,and they can not be operated at high speed of the trains play a better role in supporting and protecting,and need to be maintained by power-stabilized vehicles.By stabilizing the car,the ballast particles are closely arranged under the action of the exciting force,which greatly increases the compactness of the track bed.The ballast particles are changed in position,and the ballasted ballast with changed geometry is restored,thereby improving the overall stability of the ballast bed,achieving the purpose of shortening or canceling the maintenance period of the slow-speed railway operation,and effectively improving the railway maintenance efficiency.This paper mainly analyzed the influence of the stabilizing device of the power stabilizing vehicle on the ballast bed-sleeper system.Studied the settlement of ballast sleepers and ballast particles under stable excitation load and the mechanical properties.The main research contents and conclusions of the paper are as follows:Based on the discrete element software EDEM,spherical particles were used to construct the sleeper according to the unit division layout;the model of ballast particles of different shapes was completed using the bonded particle model;A slab was added between the track bed and the sleeper to apply downforce to the track bed,while transfer and feedback the data between the track bed and sleepers.Based on the discrete element-finite element coupling model of the sleeper-track bed,the contact force distribution between the sleeper and the ballast and the stress distribution law at different excitation frequencies are obtained.By analyzed the change between the bottom of the sleeper and the ballast,the settlement of the track bed was analyzed the relationship between the amount and the excitation frequency was used to obtain the sleeper settlement and the ballast particle movement distribution during the stable operation process.The dynamic characteristics of the track bed under the stable excitation operation are studied and analyzed.Analyzed the motion distribution law of ballast particles in the stability process,and the effects of different excitation frequencies on the mechanical characteristics of ballast bed settlement.From the ballast particles and sleepers,the principle of ballast bed settlement was analyzed from microscopic.Explored the changes of the mechanical direction of ballast particles in different areas,ballast settlement and ballast acceleration under different excitation frequencies.Build a ballast box test platform to simulate the stable operation of a ballast bed with a dynamic stabilizing device,and obtain the effects of different excitation frequencies on the ballast settlement and other mechanical characteristics during the stable operation.The results showed that within the range of normal operation and stable operation,as the stable operation progresses,the amount of settlement of the track bed continues to increase.When the compaction of the track bed ballast reaches a stable stage,the amount of settlement of the track bed tended to stabilize;with the excitation frequency the increase of the sleeper's settlement increased first and then decreased.For the ballast box test platform,when the excitation frequency was 36 Hz,the amount of settlement was the largest,indicating that the stabilization operation of the excitation frequency had the best stabilizing effect on the track bed.The correctness of the discrete element-finite element model was verified by comparing the results of the test and simulation of the changes in the track bed settlement.The results showed that due to the irregular characteristics of the ballast particle shape,it is correct and effective to use the unbreakable bond particle model to approximate the construction of sleepers and ballast models.As the stable operation progresses,the bottom of the sleeper and the ballast shoulder were under greater stress and the vibration fluctuations were larger.At the same time,the amount of sleeper settlement increased significantly.When the stabilization operation was carried out for a period of time,the force between the bottom of the sleeper and the ballast decreased,indicating that the sleeper and the ballast particles were in tight contact,and the track bed had reached a stable state.The ballast under the ballast shoulders on both sides was displaced in the same direction as the sleeper,but the ballast particles directly under the sleeper always moved downward,due to the sleeper.When the excitation frequency was between 30 Hz and 36 Hz,the cumulative settling amount of the track bed gradually increased with the increase of the excitation load frequency;when the excitation frequency exceeded 36 Hz,continuing to increase the excitation frequency for stable operation instead cause the track bed the amount of settlement was reduced.