Research On Mechanical Properties Of Ballast Track Wetting Bed

Ballasted track is one of the important track structures of high-speed railway,but as a kind of granular structure,the ballasted track will be broken,powdered and dirty under the action of high-speed train cyclic load.Under the effect of rainfall weather,water will gradually form inside the ballast bed,which reduces the friction between ballast particles and the resistance of ballast bed.In serious cases,it will lead to the formation of slurry between pulverized coal cinder and water to wrap the ballast and form the consolidation of ballast bed,which seriously affects the service performance of ballast bed.Therefore,the research on the mechanical properties of ballasted track under rain conditions is an important guarantee to maintain the stability of the service performance of ballasted track under complex weather conditions.The contact forms of crushed stone ballast vary.The contact parameters of ballast are highly discrete due to the influence of material,shape and gradation.When the rainwater is immersed in the ballast bed,the original contact relationship between ballast particles will be changed.At the same time,it interacts with dirty particles to produce cohesive effect,which has a significant impact on the mechanical properties of the ballast bed.At present,most of the researches focus on the macroscopic drainage problems of the ballast bed,and lack the research on the micro mechanical mechanism of the wet ballast particles in the humidified ballast bed.Based on the key project of National Natural Science Foundation of China(United fund of high speed railway),"Research on degradation mechanism of high speed railway bulk ballast bed"(U1234211)"for extended research,this paper introduces surface energy as the characterization parameter of cohesive contact between wet ballasts,and takes the lead in adopting cohesive contact model between wet ballasts,To solve the scientific problem that the contact relationship of traditional discrete element can not accurately simulate the wet ballast,and based on the test principle of multi parameter response surface method,combined with the angle of repose test,the key parameters of wet ballast are calibrated and verified.Through the combination of theoretical analysis and numerical simulation,the mechanical properties of wet ballast are studied,and the influence of dirt on its mechanical properties is explored.The main research of this paper is summarized as follows:1.The wetting ballast bed model of ballasted track based on cohesive contact constitutive model is establishedBased on the three-dimensional laser scanning technology,the real shape of the ballast is obtained to realize the accurate simulation of the real shape of the ballast particles;The surface energy between particles is introduced to characterize the bonding between wet particles,and the JKR cohesive contact model is used to establish the wetting track bed model,which can accurately simulate the contact state of ballast after rainwater immersion in the track bed;Based on the response surface method,the contact parameters of wet ballast are determined according to the angle of repose test,and the accuracy of the wet ballast model is verified by the measured lateral resistance of the ballast bed.2.Study on mechanical mechanism of ballast track wetting bedBy establishing the discrete element simulation model of ordinary track bed and humidified track bed for comparative analysis,the distribution and transmission law of internal stress and vibration of humidified track bed are analyzed from the micro level,and the changes of cumulative settlement,lateral resistance and support stiffness of humidified track bed are studied from the macro level,revealing the mechanical mechanism of humidified track bed,According to the response surface method,the contact parameters of ballast under different water content are calibrated,the influence of water content on the mechanical properties of clean ballast bed is analyzed,and the maintenance suggestions of clean ballast bed are put forward.3.Influence of ballast fouling on mechanical properties of humidified ballastThrough the establishment of humidified ballast bed model,dirty ballast bed model and dirty humidified ballast bed model,the influence of two kinds of deterioration on the mechanical properties of granular ballast bed was analyzed;The influence of soiling rate,moisture content of soiling particles and soiling particle size on the mechanical properties of ballast bed was systematically studied.The changes of internal stress and vibration attenuation rate of soiling humidified ballast bed were explored.The deterioration mechanism of soiling humidified ballast bed was revealed,and the suggestions of soiling limit for cleaning operation were put forward.4.Study on the influence of train speed and axle load on the mechanical properties of ballast bed under different conditionsThis paper systematically studies the mechanical properties of common track bed,humidified track bed,dirty track bed and dirty humidified track bed under different driving speeds and train axle loads,compares and analyzes the stress characteristics,vibration characteristics and cumulative settlement variation rules of different track beds,and puts forward maintenance suggestions for high-speed railway,heavy-duty railway and railway operation in areas with large annual rainfall.