Study On Force Transfer Characteristics Of Granular Ballast Of CWR On Ballasted Track Bridge

Because of the ballast bed’s discreteness,the ballast bed’s resistance is non-uniform After the sleeper movement,the ballast bed will change in the state of compactness and other conditions,which will eventually lead to the instability of the ballasted continuous welded rail(CWR)on the bridge.In the study of the track-bridge interaction of the ballasted CWR on the bridge,the traditional research method is to use simplified linear or non-linear spring to simulate the resistance of the ballast bed.This method can’t obtain the movement and distribution of particles,and it is difficult to conduct in-depth research.Therefore,it is necessary to introduce the discrete element method to analyze the mechanism of ballast action between beam and rail from a microscopic point of view,and to study the longitudinal mechanical behavior of the ballasted CWR on the bridge.The specific research contents are as follows:(1)Using the multi-scale theoretical model of granular materials based on the macroscopic continuum-meso-discrete model,a mesoscopic discrete model with six sleepers is established,and the local part of the 32m simply supported beam macroscopic continuum model is analyzed by window movement(2)When establishing the discrete element model of gravel ballast bed,the ballast particles are simulated by using spherical particles based on reasonable simplified method and considering the computational efficiency of the discrete element.According to the requirements of the special grade grading,the "falling rain method" is used to layer the spherical particles that meet the grading regulations,and the stratified tamping is used to compact the ballast bed.The wall is used to simulate the sleeper.Because the wall has no weight in the EDEM,it needs to be programmed by the API interface of the EDEM software,and an automatic iterative algorithm is introduced to apply gravity to the sleeper.The model was subjected to parameter calibration and reliability verification using the angle of repose and the resistance of the ballast bed(3)First,the discrete element model of gravel ballast bed is established by using the discrete element method.The force transfer characteristics of ballast bed on bridge under different track-bridge interaction conditions are studied,and the mechanism of ballast bed between beams and rails is analyzed from a mesoscopic-perspective.Finally,by introducing the coupling method of finite element and discrete element,the local discrete element model of the movable end of the simply supported beam and the 32 m simply supported beam discrete element model are established to study on force transfer characteristics of granular ballast of CWR on ballasted track bridge.(4)It is found that for the ballasted CWR on the bridge,it is necessary to pay attention to the influence of the ballast bed state on the track-bridge interaction.In the process of temperature cycle,the energy dissipation exists in the ballast bed.Under different track-bridge interaction conditions,the particles between two sleepers at the movable end of the simply supported beam are most susceptible to disturbance.During the maintenance of CWR on ballasted track bridge,special attention should be paid to the state of the ballast bed in the area of the movable end of the simply supported beam.