Study On The Influence Of Needle-Flaked Ballast On The Tamping Effect Of Ballast Bed

Ballast bed is composed of ballast particles,which has a certain elasticity and can play a role in buffering vibration reduction and noise reduction.However,with the increase of service time,the ballast bed will undergo settlement deformation and reduce its compressive performance.At this time,by tamping the diseased ballast bed,the mechanical properties of the ballast bed can be effectively restored,thereby prolonging the service time of the ballast bed.In the tamping operation,the key to tamping is the interaction between the tamping picks and the ballast particles,and because the ballast in the ballast bed has different shapes,different ballast beds show different initial states,so the tamping effect is not the same.In particular,the content of needle-flaked ballast,which is a deformed ballast,has a great influence on the mechanical properties of the ballast bed itself.Therefore,the mechanical characteristics of aggregates containing needle-flaked ballast can be analyzed to summarize the influence of needle-flaked ballast on the vertical compressive capacity of the track bed.At the same time,in the tamping operation of the track bed under different needle-flaked ballast content,the tamping parameters are optimized for different tamping parameters,which can effectively improve the tamping quality of the ballast bed.The main research content and results of this paper are summarized as follows:(1)Study on compressive characteristics of needle-flaked ballast.Through discrete element simulation and physical experiments,the compressive characteristics of ballast under different needle-flaked contents were analyzed.The results showed that the increase of needle sheet index reduced the compressive capacity of the track bed,and the influence of needle ballast,needle-flaked ballast and flake ballast on the compressive characteristics of the track bed increased sequentially.(2)Creation of ballast bed tamping model and analysis of tamping mechanism.Four groups of ballast bed models with different needle-flaked mixed ballast content were designed and created by discrete element method,and the vibration frequency,vibration amplitude and interpolation speed of the tamping pickaxe were selected as the main parameters of the tamping operation,and the porosity,coordination number,average particle velocity and vertical resistance were selected as the evaluation indicators to evaluate the tamping effect of the ballast bed,and the tamping mechanism of the tamping operation was analyzed by simulating the ballast bed model.The results show that the tamping operation can effectively improve the compactness under the sleeper of the ballast bed and enhance the vertical stiffness of the ballast bed.(3)Optimization analysis of ballast bed tamping parameters under different needleflaked ballast content.By simulating the tamping of four groups of ballast beds with different needle-flaked ballast content,the tamping effect of each group of ballast beds was analyzed,and the tamping parameters of the track bed under different conditions were optimized.The results show that the vertical stiffness of the ballast bed can be improved by tamping operation,but with the increase of needle-flaked ballast,the suboccipital compacting effect of the ballast bed will decrease and the vertical compressive ability of the ballast bed will be weakened.In order to make the tamping effect of the ballast bed under different conditions reach a better level,when the density of the ballast bed with less needle-flaked ballast content is high,the tamping parameters are selected as high frequency and low amplitude,and the ballast bed with more needleflaked ballast content is selected with low frequency and high amplitude,and the interpolation speed needs to comprehensively consider the tamping effect and tamping efficiency,and the value of 1～2m/s is appropriate.