| The ballasted railway is one main structure of global railway system and has been widely used in the ordinary-speed railway,heavy haul railway and high-speed railway systems because of its good adaptability and low construction cost.Ballasted bed lateral resistance is one of the necessary conditions for keeping the train running safely and smoothly and control the position of rail in ballasted railway CWR lines;It is mainly affected by rail temperature change,fastener,sleeper,ballasted bed parameters and maintenance.However,as the railway systems develop towards a higher-speed and more massive load situation the track system puts forward higher requirements for the longitudinal and horizontal stability of ballasted track,which means using conventional mono-block sleepers may cause the lack of ballasted bed lateral resistance.Besides,because of the discrete features of ballasted bed,the finite element method can not well reflect the contact state and contact force distribution of ballast particles,resulting in a relative lack of research on the ballast-sleeper interaction.In consideration of the problem ofpotential insufficient lateral resistance of ballasted bed and the shortcomings of current research,the global research and reinforcement solutions of ballasted bed lateral resistance are comprehensively analyzed in this paper,and the Chinese ?c concrete sleeper is optimized to form three kinds of winged sleeper and three kinds of frictional sleeper.A brand new full-scale ballasted bed model with 8 meters length was built,the lateral resistance single tie push tests were carried out to study the lateral resistance of the IIIc type concrete,the optimized sleepers,the bi-block sleeper and the ladder sleeper.In addition,based on the discrete element method and three-dimensional scanning,three-dimensional ballasted bed-sleeper models were used to analyze and study the microscopic characteristics of the lateral resistance of the ballasted bed.The main work and results of this paper are as follows:1.The ballast bed lateral resistance of the mono-block concrete sleeper is studied through the real-scale model tests.Actual lines usually adopt measures such as increasing shoulder width and shoulder height to enhance the lateral resistance of the ballasted track.However,the tests and comparison of ballast bed lateral resistance under different shoulder width and shoulder height are relatively scarce;Most ofthe research were based on the finite element method.In view of the above deficiencies,a new experimental real-size model with 8 meters length was built to study the influence of shoulder ballast size and sleeper length on mono-block sleeper lateral resistance.2.The shape of the ?c sleeper was optimized,and the ballast bed lateral resistance tests were carried out.The ballast bed lateral resistance is the force of the ballast particles against the lateral movement of the sleeper;And it can mainly be divided into sleeper bottom resistance,sleeper side resistance(crib resistance)and sleeper end resistance.In order to increase the lateral shear reaction of the ballast against the movement of the sleeper,three winged sleeper types were designed by adding bumps(winged parts)to the side or bottom of the ?c type sleeper.In order to increase the frictional interaction between the ballast and the bottom of the sleeper,three types of frictional sleeper were designed by adding small frictional pieces or stripes to the bottom of IIIc type sleeper.Based on the lateral resistance single tie push tests,the ballast bed lateral resistance of each type of winged sleepers and frictional sleepers were studied and compared with the lateral resistance of ?c type sleeper.3.The ballast bed lateral resistance of bi-block sleeper and ladder sleeper were tested,The bi-block sleeper and ladder sleeper which are composed of two concrete blocks and steel profiles are different from the conventional mono-block sleeper.The action mechanism of the bi-block sleeper and ladder sleeper is different from that of the mono-block sleeper when laying on ballast bed.In this paper,the real-mode model ballast bed lateral resistance tests of bi-block sleeper and ladder sleeper are carried out.Then the lateral resistance comparison between bi-block sleeper and the ?c sleeper was carried out,and the resistance distribution characteristics of ladder sleeper were studied.4.Developed a DEM fast modeling method for ballast aggregateThe ballast bed is a collection of ballast particles.The discrete element method can better reflect the contact and occlusion state of the ballast particles of the ballast than the finite element method.However,with the improvement of the simulation precision of the ballast particles and the enlargement of the model size,using the existing modeling methods such as the falling rain method and the radius expansion method to establish a high-precision three-dimensional ballast bed model is characterized by long time-consuming,uncontrollable porosity,discontinuous gradation and other shortcomings.Considering the above shortcomings,a modeling method combining particle replacement and stress relaxation is developed based on three-dimensional scanning using discrete element software PFC3D.The model of the ballast aggregate can be quickly established,the porosity is controllable,and the gradation is continuous.5.The three-dimensional sleeper-ballast bed models of each type of sleepers were established.The ballast bed lateral resistance mesoscopic characteristics of each type of sleepers were studied.The research on the ballast bed lateral resistance focus on the macroscopic numerical analysis while the mesoscopic characteristics such as the number,size,distribution of the contact between the sleeper and ballast bed and the contact force bond distribution inside ballast bed when the sleeper is laterally moved are relatively scarce.In this paper,the three-dimensional sleeper-ballast bed models are established.Then the sleeper-ballast contact state of the IIIc type sleeper,all kinds of the winged sleeper,various types of the frictional sleeper,bi-block sleeper and ladder sleepers and the force distribution characteristics of ballast particles inside ballast bed are studied.This article contains the 89 figures,34 tables and 108 references. |
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