Study On Dynamic Characteristics Of The Accumulated Ballast And Its Elastic Cushion Optimized Structure Of Ballasted Track

As a main track structure,ballasted track is widely used all over the world because of its good elasticity,excellent vibration reduction effect and easy maintenance.However,under the long-term action of load,the diseases such as ballast bed crushing,uneven settlement,mud pumping and so on are more serious.With the increase of train speed,the wheel rail impact is intensified,which further aggravates the disease of ballasted bed.These seriously restrict the popularization and application of ballasted bed.It is of great significance to study the dynamic service characteristics of ballast ballast and optimize the design of ballast to reduce the disease.With the help of indoor multifunctional dynamic loading device and edem discrete element software,this paper focuses on the dynamic performance of ballast and its elastic cushion optimized structure.This paper studies the crushing law of ballast,vibration response law and the energy consumption behavior of the accumulated ballasts.The specific research contents and results are as follows:(1)The impact load tests with different frequencies are carried out for the accumulated ballasts,and the dynamic characteristics and other response laws of the accumulated ballasts are studied.Impact loads of 13.5hz,27 Hz,45Hz and 90 hz were used in the test.The crushing and deterioration law,vibration response,vibration damping characteristics,dynamic stiffness and energy consumption characteristics of ballast samples are studied and analyzed.The results show that the frequency will increase the crushing and cumulative settlement deformation of the ballast,increase the dynamic stiffness and reduce the hysteretic energy consumption effect of the sample,but it has a low impact on the vibration reduction characteristics of the ballast structure.(2)By comparing the different layout of elastic cushion,the influence of elastic cushion on the dynamic characteristics of ballast is studied.Comparative tests were carried out on the samples of top layer,middle layer,bottom layer and middle and lower double layers.The test results show that the buried depth of the elastic cushion is about small,the more the number is arranged,the lower the dynamic stiffness,the greater the damping ratio and the smaller the crushing index of the optimized structure;The position of elastic cushion has a great influence on the vibration response of ballast,attenuates the vibration of ballast in the lower part of cushion,and enhances the vibration of ballast in the upper part of cushion;Compared with the traditional ballast,the acceleration transmission rate of the top and middle structures is reduced by-10 d B,and the vibration reduction effect is enhanced.(3)The influence of elastic modulus and thickness of elastic cushion on the dynamic performance of ballast structure is analyzed.The tests were carried out with 5mm,10 mm,15mm,1MPa,6Mpa,10 MPa and other elastic cushions.The results show that the parameters of the cushion have little change on the performance of the optimized structure.The overall law is that the lower the elastic modulus and the greater the thickness of the cushion,the smaller the dynamic stiffness and the greater the damping ratio of the optimized structure,and the fuller the hysteretic curve.At the same time,the stronger the enhancement effect on the vibration of the upper particles,but the change rate of the above indexes is within 10%.(4)Based on EDEM discrete element simulation platform,the simulation model of the accumulated ballasts and its optimized structure is constructed,and the meso behavior of the accumulated ballasts and optimized structure is studied.The research and analysis are carried out from the perspectives of the average contact force of particles,the distribution and change of kinetic energy,the characteristics of velocity and flow field,and the relevant conclusions in the indoor test are verified.