Research On Train Load Transfer Characteristics And Mechanism In Ballastless Track Of High-speed Railway

China’s high-speed railway is in a critical period of high-quality development.With the accumulation of operating experience and in-depth research of high-speed railway,the technical systems and standard systems are gradually improving.As the key factor for design and maintenance of ballastless track,train load needs to be further studied in combination with engineering and operational practices.There are still many problems in the current research on train load transfer.For example,the study of train load effect on ballastless track mainly focuses on stress and vibration analysis,and lacks train load transfer characteristics;In the design and simulation analysis of ballastless track,always concerned the track structure itself,but most of the ballastless track diseases on site are due to the interaction with the lower foundation,so the multi-layer structure system should be integrated;the train load diagrams of ballastless track has not been formed in China,the research on train load transfer in ballastless track is still based on the technical route of ballasted track;the current tests are mostly at special locations on the surface of tracks,and lacks of the continuous test on the train load transfer process in ballastless track.This paper was based on train load transfer process,established static and dynamic multi-layer structure system integrated analysis model of ballastless track and subgrade.Developed a piezoelectric continuous test system for train load transfer testing.By the combination of static and dynamic analysis,as well as the full-scale model test and field running test were carried out to study the transfer characteristics and mechanism in the process of train load transfer.Proposed the train load diagrams for ballastless track.And the optimization suggestions of ballastless track were proposed from the train load transfer characteristics.The specific research contents and results are as follows:(1)The establishment and verification of the static and dynamic multi-layer structure system integrated analysis model for train load transfer.By investigating the function of different types of ballastless track,track limit device,contact state of layers,and the actual mechanical parameters of the vehicle,ballastless track and subgrade.To the study of train load transfer,the train dynamic model,different types of ballastless track model,subgrade model were established.The train load transfer static and dynamic multi-layer structure system integrated analysis models were established respectively,and the rationality and reliability of the models wereverified by comparing with the data of lab test,field test and Wuhan-Guangzhou comprehensive test.In addition,the simulation software was developed to improve modeling and results analysis efficiency.(2)Research on static transfer characteristics and mechanism of train load in ballastless track of high-speed railway.Used the static train load transfer model established,based on the train load transfer process.To different types of ballastless track in turn study the static distribution characteristics and influence factors of rail supporting force,train load transfer path and range in ballastless track,the distribution characteristics of inter-layer stress and displacement,the distribution characteristics of layer stress and displacement on subgrade.Obtained the distribution characteristics of wheel load distribution ratios under different types of ballastless track and influencing factors.Defined the expansion area and homogenization area of train load transfer.Obtained the path and range of train load transfer,and the distribution characteristics of stress and displacement of each layer of ballastless track and subgrade.Analyzed the difference train load transfer characteristics and mechanism of different types of ballastless track,and put forward the correlation between the wheel load distribution ratio and the track stiffness,the correlation between the train load transfer characteristics in ballastless track and the middle layer and inter-layer contact state,the correlation between the train load transfer characteristics in subgrade and the track unit or longitudinal distribution.(3)Research on dynamic transfer characteristics and mechanism of train load in ballastless track of high-speed railway.Used the dynamic train load transfer model established,based on the train load transfer process.To different types of ballastless track in turn study the dynamic distribution characteristics and the speed influence of rail supporting force,wheel-rail dynamic response,dynamic stress and vibration characteristics of track and subgrade.Defined the main load bearing and vibration area of train load transfer.Obtained the distribution characteristics of dynamic stress and acceleration of train load in different types of ballastless track and subgrade.Put forward the suggestion of the damage prevention and control in the region with larger stress and vibration.(4)Research on train load comprehensive test in ballastless track of high-speed railway.The principles of train load transfer test was put forward through investigation and theoretical calculation.Based on the principles of piezoelectric test,improve theshortcomings of poor adhesion between piezoelectric sensors and concrete,and a large number of arrangements affects the force of ballastless track.Stone-based piezoelectric sensor and force-measuring pad were developed,and test system and calibration method were developed to provide technical support for laboratory and field tests.The laboratory full-scale double block sleepers ballastless track train load transfer comprehensive test and the Beijing-Shenyang CRTS Ⅲ ballastless track load transfer driving test were carried out respectively.Trough tested the distribution characteristics of rail supporting force and structure stress of double block sleepers ballastless track and CRTS Ⅲ ballastless track were obtained.Compared with the simulation results,proved the reliability of the test method and test system.(5)The application of train load transfer laws on train load diagrams and structural optimization on ballastless track.Based on the research results of train load transfer characteristics and mechanism of ballastless track,the application research were carried out.Train load diagrams research,by compared and analyzed the train load effect of ballastless track under the current mainstream models of high speed-railway in China,mastered the correlation between the effect characteristics and train load parameters.The train load diagrams and loading position of ballastless track of high-speed railway were proposed,and analyzed the dynamic coefficient and the adaptability of train load diagrams.Structural optimization research,applied the ballastless track load effect of train load diagrams.The influence of foundation stiffness,structure size,inter-layer contact state and structure stiffness on train load transfer characteristics of ballastless track were studied.According to the train load transfer laws under different conditions,put forward the suggestions for ballastless track structure optimization.