Study On The Impact Of Ballast Grading On Tamping Effect

Tamping operation is an important maintenance process of the ballasted railway.With the development of railway towards the direction of high speed and heavy load,the maintenance and repair work is becoming heavier and heavier.In order to improve the tamping effect,the important solution to the problem rests with the choice of suitable tamping parameters.However,due to the lack of key technology of tamping machine in China,the choice of tamping parameters depends on practical experience and spot test.Many studies,too,have only optimized the tamping parameters in the specific state of the ballast bed,without taking the effect of ballasted grading with the best tamping parameters into consideration.Therefore,in this paper,the ballast-bed tamping operation system,as the research object,combined with the means of discrete element method and experiment,is applied to study the selection law of different grading bed on tamping parameters.Two parameters of tamping frequency and amplitude of the main action of tamping are designed as variables,and the compaction effect is evaluated by the compactness of the ballast bed and broken volume of ballast.Firstly,the graded beds of ordinary railway and high-speed railway are selected and calibrated to A and B grading bed,and the analysis model of tamping operation in ballast bed is established by using the discrete element method,then the method of vertical stiffness test has been used to compared ballast bed model which is composed of broken ballast or unbroken ballast.The model that is closer to the real bed state has been selected to make comparison.Design of simulation scheme based on response surface CCD method uses selected model to simulate the tamping operation Process under different tamping frequency and amplitude.Finally,the response surface regression model for the compactness of the ballast bed and Broken volume of ballast are established,and the optimum tamping parameters of two kinds of graded ballast beds are obtained,as well as the influence law of the frequency and amplitude of the ballast bed grading is acquired.According to the study,the ballast bed model which is composed of broken ballast can reflect the performance of the actual ballast bed more accurately.At the same time,the research results show that there are differences among the optimum tamping parameters of varied graded beds,and the high frequency and low amplitude tamping compaction is preferable when the ballast bed gradation is relatively wide,and the low frequency and higher amplitude tamping compaction is more suitable when the ballast bed gradation is relatively narrow.Secondly,in the process of tamping,the broken volume of ballast of the wide-graded ballast bed is relatively small,and the broken volume of ballast of the narrow-graded ballast bed is relatively large.These results can provide a reference for the selection of working parameters of the tamping device of different grading ballast bed.