Study On Subgrade Reinforcement And Track Transition Measures For Laying Ballastless Track In The Turnout Area Of High Speed Railway With Ballasted Track

With the implementation of the "Western Development" strategy,the construction of high-speed railways in the western regions of China has seen vigorous development.However,due to the complicated drainage system and the unique engineering geological conditions in the northwest region,it is difficult to maintain the geometric shape of the line in the turnout area of the newly built high-speed railway station with ballasted track,and there is rapid deformation in the operation stage,which increases the workload and difficulty of maintenance and repair in the later stage.In order to minimize the roadbed diseases that affect the traffic safety after railway operation,ballastless track can be laid in the turnout area to ensure the safe and smooth operation of vehicles.This project plans to carry out research on the reinforcement of ballasted track subgrade and measures for track transition section in conjunction with the ballastless transformation project of Beitan Station on the China Lanzhou Railway.At present,the foundation of the embankment in the turnout area of the station has been treated with cement soil compaction piles,and the subgrade has been filled to the top surface of the bottom layer of the subgrade bed.This paper mainly focuses on the reinforcement of the subgrade that has been filled to the top surface of the bottom layer of the subgrade bed,and verifies whether the reinforced subgrade meets the requirements for laying ballastless track,Study the treatment measures for the transition section of ballasted ballastless track and optimize the transition measures when the transition section of ballasted ballastless track is connected with the existing transition section of road and bridge.The research results can provide a basis for the proposed ballastless track laying in the switch area of Beitan Station of Zhonglan Passenger Dedicated Line.The main research work is as follows:(1)Review literature and on-site engineering data to understand existing subgrade settlement control methods,settlement prediction and analysis models,and previous treatment measures for the transition section of ballasted ballastless track,and determine treatment measures for subgrade reinforcement of ballasted track high-speed railway and treatment measures for the transition section of ballasted ballastless track.(2)Using ABAQUS finite element software,establish a vehicle track subgrade coupling dynamic model for the transition section between ballasted track and ballastless track in the turnout area of high-speed railway,determine the parameters of the dynamic model and the contact mode of wheel rail,and verify the correctness of the model.(3)Different treatment measures were taken to reinforce the roadbed that has been filled to the top surface of the bottom layer of the roadbed in the turnout area of the high-speed railway with ballast track.The settlement of the roadbed after reinforcement was monitored on site,and the settlement law of the roadbed after reinforcement was analyzed;Select a settlement prediction method with good stability,high accuracy,and suitable for the interaction between loess and fine sand layers,and conduct settlement prediction analysis on the reinforced roadbed to determine the final settlement amount;Based on the preloading time of on-site preloading load,verify whether the subgrade settlement after reinforcement meets the requirements for laying ballastless track.(4)Studied the dynamic response of the vehicle rail system for the graded transition of fastener stiffness,the transition of ballast adhesive cured track bed,and the combination of graded transition of fastener stiffness and the transition of ballast adhesive segmented solidified track bed;Firstly,the dynamic model of the transition section between ballasted and ballastless track is established for the graded transition measures of fastener stiffness,and the influence of the graded transition of fastener stiffness and the length of the transition section on the dynamic performance of the vehicle track system is analyzed;Secondly,the dynamic model of the transition section between ballasted and ballastless track in which the ballast glue solidifies the ballast bed in sections is established,and the influence of the differential value of the subgrade angular settlement,the angular settlement length and the length of the transition section on the dynamic performance of the vehicle track system is analyzed;Finally,the dynamic analysis model of the transition section of ballasted ballastless track is established for the joint measures of the graded transition of fastener stiffness and the transition section of ballast adhesive curing track bed.The impact on the dynamic performance of the vehicle track system when the train runs in both directions and the length of the transition section is 20 m and 30 m is analyzed,so as to conduct dynamic research on the impact parameters of different treatment measures.(5)Establish a vehicle track subgrade coupling dynamic model connecting the ballasted ballastless transition section and the road bridge transition section,analyze the dynamic response of the ballasted ballastless track transition section under the combined measures of fastener stiffness graded transition,ballast adhesive curing track bed transition,and fastener stiffness graded transition and ballast adhesive curing track bed transition,and compare and analyze the dynamic response results of different treatment measures,In this way,the optimal treatment scheme for the transition section of ballasted ballastless track when multiple transition sections are connected is determined,and the reasonable setting length of the transition section of ballasted ballastless track is determined.