Research Of Ballast Bed Longitudinal Resistance Characteristics And Reinforcement

Railway is an important mode of the world’s transportation,and ballasted track is its main form.With the development of high-speed railways,continuous welded rail(CWR)tracks have emerged.Nowadays,CWR Track have almost become a required structure for railways.The CWR eliminates the traditional rail joints,which greatly improves the smoothness of the track,thereby increasing the operating speed of the train.However,after the long rail is locked,a large temperature force will accumulate inside the rail,and it will also be subjected to the starting force,braking force,traction force and other stresses from the train.These forces together constitute the longitudinal force inside the rail.In order to resist the longitudinal force of the rail and maintain the overall stability of the track structure,the track bed needs to provide sufficient longitudinal resistance.Therefore,the longitudinal resistance of the ballast bed is a decisive index of the stability of the ballasted track.In recent years,with the further development of high-speed and heavy-haul railways,the longitudinal force acted to the CWR track has become greater and greater,and higher requirements have been placed on the longitudinal resistance of the ballast bed.Based on this background,this article summarizes the previous studies on the longitudinal force of the CWR,and clarifies the principles and laws of longitudinal force generation.Afterwards,the relevant home and abroad researches on the resistance of the ballast bed were reviewed,and the research on the influence factors of the ballast resistance and the enhancement measures were analyzed,forming the research ideas and content of this article.This article first conducts an experimental study on the longitudinal resistance of a single sleeper to explore its influencing factors and characteristics.On this basis,the resistance enhancement optimization of the commonly used type III concrete sleepers in China is carried out,and the steel rod-reinforced sleepers and the arrow shading frictional sleepers are designed and tested.An indoor full-scale test model of the track panel-ballast bed was laid to test and explore the longitudinal resistance characteristics of track panel.Finally,the discrete element method is used for numerical simulation,and the mechanism of the longitudinal resistance of the ballast bed is analyzed in a mesoscopic view.The main work and results of this paper are as follows:1.The longitudinal resistance characteristics of the track bed of a single sleeper were explored through experiments.The test is an important method to study the resistance characteristics of ballast bed.The required value of the ballast bed resistance in Chinese relevant standard is formulated for a single sleeper.For example,the standard requires that the longitudinal resistance of the ballast bed should be greater than 14 k N/sleeper.Therefore,this article first conducted a series of experiments to study the influencing factors of the longitudinal resistance of a single sleeper,and clarified the influence of the crib ballast fullness,the width and height of the ballast shoulder on the longitudinal resistance of the single sleeper.The contribution of longitudinal resistance of single sleeper points out the direction for the subsequent further research.2.Design new sleepers to enhance the resistance of the track ballast bed,and conduct experiments and investigations.In order to enhance the ballast bed longitudinal resistance,this article summarized the past research experience and designed steel rod-reinforced sleepers and three arrow shading frictional type sleepers,based on the type III concrete sleepers.The resistance enhancement effect and influencing factors were tested and determined.Finally,combining the characteristics of sleepers,suggestions are made for its application in actual railway lines.3.Explore the longitudinal resistance characteristics of the track panel through tests.In actual lines,the track often maintains the stability of the track bed in the form of a track panel.In this paper,an indoor full-scale test model of the track panel-ballast bed is built,and the overall characteristics of the track panel longitudinal resistance are studied through experiments.At the same time,the influence of the fullness of the crib ballast,the number of sleepers and the sleeper spacing on the longitudinal resistance of the track panel is explored.Therefore,feasible suggestions for actual design,installation and maintenance were put forward.4.Establish a model based on the discrete element method and perform numerical simulation analysis.Experimental research focuses on the summary of macroscopic laws,while numerical simulation analysis starts with mesoscopic analysis of the mechanism.This paper establishes a sleeper-track bed three-dimensional model,uses the discrete element method to simulate the longitudinal resistance of type III sleepers and arrow shading frictional sleepers,and analyzed the force chain distribution during the longitudinal displacement of the sleeper.The microscopic mechanism of the longitudinal resistance of the ballast bed was also explored.This thesis contains 74 figures,17 tables,and 133 references.