Study On Mechanical Properties And Parameter Optimization Of Tamping On High Speed Ballast Railway

The tamping operation is an important component of ballast railway maintenance,which plays an important role in improving ballast compactness,increasing track stability and ensuring safety operation of train.With the development of high speed railway,under the action of high speed dynamic load,the vibration and impact of railway track is more obvious,the requirement of railway track is more stringent,and the requirement of tamping operation is more accurate.Because the ballast is a particle structure which is composed of graded crushed stone,with non-linear response and self-organized behavior and other complex mechanical properties during tamping process,which has brought some difficulties to research the mechanics mechanism of tamping operation,the selection of tamping parameters usually depends on practical experience and field test,and lacks corresponding theoretical basis.Therefore,the mechanical behavior of ballast and its changing law and the influence of tamping parameters on tamping effect during tamping process were studied in depth,which has great theoretical significance to study the mechanics mechanism of tamping,and great practical value to accurately select tamping parameters and effectively improve tamping effect.In order to study the mechanics mechanism of tamping,accurately select tamping parameters and effectively improve tamping effect,firstly,the compact mechanism of tamping operation and the influence of tamping parameters on tamping effect were analyzed theoretically.Then,the mechanical behavior of ballast and its changing law during tamping process were tested and analyzed by physical test and numerical simulation respectively,and the mechanical properties of tamping operation were studied from the mesoscopic scale.Then,the response surface method was used to construct the response surface of tamping operation,the model was used to optimize tamping parameters,and the prediction model of tamping parameters was established by using the combination prediction method,which laid the foundation for accurately selecting tamping parameters.Finally,by introducing the parameter adaptive mechanism,a variable tamping parameter was proposed to improve the effect of tamping operation,which provides a new research idea for the selection and optimization of tamping parameters.The specific research contents are as follows:1.Based on vibration compaction theory,the working principle of tamping operation on ballast railway was analyzed,and the mechanical model of tamping operation was proposed.The compact mechanism of tamping operation and the influence of tamping parameters on tamping effect were analyzed theoretically.The function relation between tamping parameters and ballast state parameters was deduced,which provides the theoretical basis for the precise selection of tamping parameters.2.Based on irrigation method and sensor test technology,ballast compactness and ballast support stiffness before and after tamping operation and mechanical behavior of ballast and its change law during tamping process,such as ballast acceleration and bottom pressure of sleeper,were tested and analyzed.According to the needs of physical test of tamping operation,the 1:1 full-size tamping test device was created.Ballast support stiffness and ballast compactness before and after tamping operation were tested in the small ballast box.The influence of tamping parameters on ballast support stiffness and ballast compactness after tamping operation is analyzed.The relationship between ballast support stiffness and ballast compactness was discussed.In the big ballast box,ballast acceleration and bottom pressure of sleeper during tamping process were tested.The change law of ballast acceleration and bottom pressure of sleeper during tamping process were analyzed,and the main factors that make the change of ballast acceleration and bottom pressure of sleeper during tamping process were presented.3.Based on granular material mechanics theory and discrete element method,the mechanical behavior of ballast and its changing law during tamping process were simulated and analyzed from the mesoscopic scale.Using the discrete element analysis method,the discrete element analysis model of ballast under tamping operation was established,and the meso-mechanical parameters of the model were calibrated by the inversion method on the basis of physical test.Using the model to simulate tamping operation,ballast compactness,ballast acceleration and sleeper force condition were extracted respectively during tamping process.By comparing the simulation results with the physical test results,it is found that they are basically consistent,which shows that the discrete element analysis model of ballast under tamping operation is effective.The evolution of ballast coordination number and contact force chain during ballast was extracted respectively.The mechanical behavior of ballast and its changing law during tamping process were further described from the mesoscopic scale.4.Based on response surface theory,combination prediction method and parameter adaptive mechanism,the optimization and prediction of tamping parameters were studied.Using response surface model,the response surface model which reflects the relationship between tamping parameters and tamping effects was created.The multi-factor and multi-objective optimization analysis of tamping parameters was carried out.The optimization analysis of tamping parameters of ballast railway with different initial states was carried out.A combination prediction method based on correlation degree was proposed to create a prediction model of tamping parameters.By introducing parameter adaptive mechanism,a variable tamping parameter was proposed,and the corresponding simulation experiment and physical experiment were carried out.The research shows that the effect of tamping operation with variable tamping parameters is better than that with constant tamping parameters,which indicates that variable tamping parameters is more reasonable than constant tamping parameters.Based on vibration compaction theory,test technology,discrete element analysis method and parameter optimization theory,the mechanical behavior of ballast and its changing law during tamping process and the effect of tamping parameters on tamping effect were analyzed systematically,which provides reference for precision tamping of high speed ballast railway.