Research On Mechanical Characteristics Of Ballast Bed Under Dynamic Stabilization

As the train develops towards the direction of high speed and heavy load,ballast track will produce ballast bed deformation,hardening and ballast particle wear,crushing and other hazards,making the track become uneven,stability of ballast bed reduced,seriously endangering the safety of the train.As a large-scale road maintenance machine,the dynamic stability vehicle is widely used in the newly-built railway and overhaul lines,which can rapidly improve the stability of the rail bed,restore the internal elasticity of the rail bed,and improve the smoothness of the track.In China,the theoretical study on the use of dynamic stabilized vehicle operation to ensure construction quality needs to be further deepened,and the influence of operating parameters on the quality of ballast bed under the operation of dynamic stabilized vehicle is lack of corresponding theoretical guidance.In practical engineering,according to existing experience,too many stable operations will lead to the quality of ballast bed,too few times and it is difficult to meet the quality requirements of ballast bed,so it is necessary to study the mechanical characteristics of ballast bed under dynamic stability.In this paper,based on the comprehensive analysis of the research status at home and abroad,according to the research needs,first carry out ballast box test,ballast box size of 1000 mm Multiplied 700 mm Multiplied 550mm(length Multiplied width Multiplied height),according to the working principle of the stable operation of the dynamic stability car,dynamic stability operation test,analysis of the mechanical characteristics of the ballast bed change rule;Then the discrete element method is used to establish a numerical model of ballast tank of equal proportion for numerical simulation analysis.By comparing with the test results,the rationality of discrete element numerical analysis is verified.Finally,a full-size numerical model of ballast bed is established to study its mechanical characteristics and variation rules under different excitation frequencies and displacement amplitudes.The main research contents and conclusions are as follows:The ballast box test platform was built to simulate the stable operation of ballast bed by the dynamic stabilization vehicle,and the mechanical characteristics of ballast bed under six frequencies of 30 Hz,32Hz,34 Hz,36Hz,38 Hz and 40 Hz were analyzed.The results show that the compactness,the accumulated settlement and the lateral resistance of the ballast bed are greatly increased in the process of stabilization,because the ballast bed becomes denser from loose state with the progress of stabilization.As the excitation frequency increases,the density,lateral resistance and settlement of the ballast bed all show a trend of increasing first and then decreasing,and the excitation frequency reaches its maximum at 36 Hz,indicating that the stabilization operation of the excitation frequency has a better stability effect on the simulated ballast test box.In order to verify the rationality and effectiveness of using discrete element software EDEM to carry out numerical analysis of dynamic stability,a discrete element simulation analysis model of equal-proportion ballast box is established,and the same excitation frequency and boundary conditions as the ballast box test are set.The simulation results show that when the discrete element model is operated at the same frequency,the simulation results and the test results have a high similarity in trend and value,and when the excitation frequency is 36 Hz,the stable effect of the ballast bed is the best.It is shown that the simulation of dynamic stabilization of ballast bed is feasible and the results are effective.On the basis of discrete element simulation analysis of ballast box,the dynamic characteristics of ballast bed under stable operation are deeply studied,and a full-size discrete element numerical simulation model of ballast bed is established.When the displacement amplitude of the sleeper is 2mm,the mechanical characteristics of the ballast bed under the stable operation of 20 Hz,25Hz,30 Hz,35Hz and 40 Hz with horizontal excitation frequency are analyzed.The results show that when the excitation frequency is 30 Hz,the stable effect of the ballast bed is the best.Then,when the excitation frequency is 30 Hz,the mechanical characteristics of the tunnel bed under stable operation are analyzed when the excitation displacement amplitude is 0.5mm,1mm,1.5mm and 2mm.The results show that the best stabilization effect is achieved when the excitation frequency is 30 Hz and the excitation displacement amplitude is 1mm.