Calibration And Application Of Ballast Discrete Element Parameters Based On EDEM

As an important research method of granular materials,the discrete element method(DEM)has been widely used for the simulation of railway ballast tracks.When the discrete element method is used to simulate the single ballast or the entire ballast bed,it can perfectly reflect the constriction and stress distribution between the ballast Particles and improve the validity of the numerical analysis.There are few studies on the systematic calibration of ballast properties using DEM.In this thesis,by carrying out ballast angle of repose test,direct shear test,uniaxial compression test,ballast box test,longitudinal and lateral resistance test,and discrete element numerical analysis,the ballast DEM Parameters are systematically calibrated from the mesoscopic scale,and the calibrated Parameters are practically applied.The main work and results of this thesis are summarized as follow:1.Systematic calibration of ballast DEM Parameters.The reliable numerical analysis relies on accurate material characteristics,and the systematic calibration of DEM Parameters in discrete element numerical analysis of ballast is now well-known.In this thesis,through a series of ballast angle of repose test,direct shear test,uniaxial compression test,ballast box test,and discrete element simulation,the ballast is calibrated for static friction coefficient,rolling friction coefficient,elastic modulus,Poisson’s ratio,restitution coefficient,etc.DEM Parameters.2.The effective factors affecting the ballast angle of repose are analyzed,and the prediction equation of the ballast angle of repose is deduced.In view of the incomplete analysis of the influencing factors of ballast material angle of repose in previous studies,this Paper conducts sensitivity analysis on Parameters such as ballast shape,quantity,and friction coefficient and establishes a series of ballast Particle angle of repose test DEM models under different variables.The influence law of each effective Parameter on the ballast angle of repose is given,and the prediction equation of the angle of repose is deduced.3.Verify ballast DEM Parameters,the longitudinal and lateral resistance test of the trackbed and the mesoscopic analysis of the resistance characteristics were carried out for the concrete IIIc sleeper and the nailed sleeper.In this thesis,based on the concrete IIIc sleeper,a nailed sleeper is designed,the longitudinal and lateral resistance test and discrete element simulation of a single sleeper are carried out,the calibrated ballast DEM Parameters are verified,and the variation law of the longitudinal and lateral resistance of the ballast bed,the number of steel bars,etc.are analyzed.The influence of factors on the resistance of the ballast bed and the distribution law of the meso-resistance characteristics,etc.4.Apply ballast DEM Parameters to establish the DEM model of the Y-shaped sleeper and the ballast bed,and analyze the resistance characteristics of the ballast bed mesoscopically.This Paper analyzes the mechanical properties of the ballast bed,the contribution of resistance,and the influence of factors such as the width of the ballast on the stability of the ballast bed through the lateral resistance test of the Y-shaped sleeper and the discrete element analysis.5.Apply ballast DEM Parameters to do establish the curve track model,and the influence of superelevation and ballast shoulder width on the stability of the curve track is analyzed in detail.Implementing the superelevation of the curved tracks is the key to counteracting the centrifugal force when the train Passes through the curve.In this thesis,the DEM model of the curved superelevation tracked is established to analyze the influence of the width of the shoulder ballast and the superelevation on the lateral stability of the curved track.