Investigation On Effect Of Manual Tamping On Ballast Track

Ballast track is a granular structure formed by the accumulation of ballast particles.Under the coupling action of train load and external environmental factors,the ballast particles are worn,broken and gradually deteriorated,and even produce diseases such as ballast settlement,unsupported sleeper,track twist overrun,track alignment irregularity etc.,which seriously threaten the safety and stability of train.The tamping can effectively rectify the above diseases,adjust track geometry,and prolong the service life of ballast line as far as possible.In the type of tamping,manual tamping is mostly used in local temporary repair and daily maintenance of the line because of its flexible and convenient characteristics.However,at present,the theoretical analysis of manual tamping lags behind the engineering practice.How to scientifically and reasonably adopt manual tamping for the maintenance and repair of ballast track is the key to improve the quality and efficiency of manual tamping and maintain the normal service performance of the line.Therefore,the action mechanism and parameter influence of manual tamping need to be investigated urgently.Based on this,this paper systematically investigates the manual tamping of ballast track by combining the methods of field experiment and numerical simulation.The specific investigation contents are as follows:(1)The field experiment of manual tamping of ballast track is carried outThe field experiment is carried out for the manual tamping of ballast track,the quality state indexes of ballast track such as lateral resistance,longitudinal resistance and support stiffness of ballast bed before and after direct insertion and tamping are tested.The experiment results show that in the process of line maintenance,direct insertion and tamping is suitable for the treatment of diseases such as unsupported sleeper and insufficient compactness of ballast bed under sleeper,so as to improve the bearing performance of ballast bed.At the same time,ballast shall be supplemented in time to ensure normal resistance of ballast bed.(2)The numerical simulation model of manual tamping of ballast track is establishedThe three-dimensional profile of ballast particles is extracted by laser scanning technology,in which the ball unit is filled to form the clump model of irregular ballast particles,and the ballast bed model is established in EDEM.Combined with Solid Works and ADAMS,the refined track structure and tamping machine model are established.In order to better simulate the contact relationship between the dispersion and the continuum,the co-simulation of discrete element method(DEM)and multi-body dynamics(MBD)of manual tamping of ballast track is realized by compiling and debugging coupling interface file.Based on the indoor and field experiment results,the accuracy of the numerical simulation model is verified and the reliability of the subsequent calculation results is guaranteed.(3)The action mechanism of manual tamping on ballast track is investigatedBased on the numerical simulation model of manual tamping of ballast track,the change of movement trend,contact relationship of ballast particles and quality state of ballast track during manual tamping are analyzed from the macro and micro point of view.It is found that the stage of inserting is the key link to achieve the purpose of tamping.In this stage,the movement trend of ballast particles changes greatly and the contact relationship is constantly reconstructed.With the progress of tamping,the compactness of ballast bed under sleeper can be increased,the contact difference between ballast particles can be reduced,the contact force distribution can be more uniform,and the force transmission path of upper load can be improved.Although the manual tamping under the condition of track lifting can rectify the diseases such as ballast settlement,track twist overrun,track alignment irregularity etc.,the quality state of ballast track is temporarily reduced after tamping.(4)The evolution mechanism of quality state of ballast track after tamping is investigatedBased on the numerical simulation model of ballast track after tamping,the simulation calculation of supplementary ballast and train loading is carried out.It is found that supplementary ballast can significantly improve the longitudinal resistance of ballast bed.Under the loading action of the train during the operation of the line,the ballast bed has large settlement in the initial stage,and the quality state of the ballast track can recover rapidly.With the continuous loading action of the train,the quality state of the ballast track can be further improved,restored and even exceed the state before tamping.(5)The influence of manual tamping parameters on the quality state of ballast track is investigatedBased on the numerical simulation model of manual tamping of ballast track,taking the compactness,lateral resistance,longitudinal resistance and support stiffness of ballast bed as evaluation indexes,the entropy weight TOPSIS method is used for comprehensive evaluation.Combined with the benchmarking comparison results,the effects of tamping parameters such as track lifting height,tamping angle,tamping depth,tamping times and tamping sequence on the quality state of ballast track are analyzed,and the parameter optimization suggestions of manual tamping are put forward.There are 101 figures,50 tables and 157 references.