Study On Dynamic Response Of Sub-grade Under High-speed Train Load

With the development of high-speed railway,ballastless track structure in China more and more common application.However,the design of the sub-grade structure of the balla stless track is not enough for the study of the dynamic characteristics and the influence parameters of the roadbed under the high-speed train load,which is based on foreign experience and large-scale simulation test results.On the basis of summarizing and absorbing the predecessors' research,this paper studies the dynamic characteristics of the ballastless sub-grade by theoretical analysis and numerical simulation.The main achievements are as follows:(1)Using the "normative law" to calculate the dynamic stress with the depth of the law and the top of the road surface generated by the dynamic deformation amplitude,the theoretical analysis of the railway sub-grade mechanism;(2)The rail structure is regarded as Euler beam,and the roadbed is regarded as isotropic visco elastic half-space.The dynamic analysis model of ballastless track and sub-grade system is established.The expression of train load in the system is obtained by Fourier series transformation.The finite element analysis is used to calculate the dynamic time history distribution of the high-speed railway sub-grade,the attenuation law of the dynamic response along the depth and the attenuation law of the power along the transverse direction.The results show that there is obvious wheel-pair effect on the dynamic of the sub-grade,and the dynamic stress in the sub-grade is decreasing along the depth and horizontal.(3)The dynamic stress distribution of the numerical calculation is verified,and the dynamic stress calculated by the norm and the dynamic stress calculated by the numerical simulation are compared with the depth and the attenuation law.The results show that the dynamic stress and numerical simulation The dynamic law of change is consistent.(4)The three-dimensional finite element model of ballastless track-subgrade system is used to analyze the influence of roadbed material characteristics,train speed and axle load on the dynamic characteristics of the system,and evaluate these parameters on the basis of this.The results show that the elastic modulus of the bed surface has little effect on the dynamic response of the subgrade.The increase of the elastic modulus of the basement bed can significantly reduce the displacement of the bed surface and reduce the vibration of the structure.Roadbed there is a greater impact.The increase of the axle load increases the dynamic stress amplitude and the dynamic displacement in the bed surface.With the increase of the train speed,the momentum and acceleration of the ballastless track increase,and the amplitude and stress amplitude of the bed Also increases,the displacement amplitude of the bed has a certain reduction;(5)In this paper,the coupled dynamic finite element model of the two-lane high-speed railway track-road system is established.The dynamic distribution and transmission law of the two-lane high-speed railway sub-grade structure along the depth direction are studied.The calculation shows that the dynamic stress and dynamic displacement of the sub-grade are increased when the train runs in opposite directions,but the acceleration amplitude is basically the same.(6)In this paper,the variation law of the single-and double-track train along the cross section is analyzed by numerical simulation.The calculation shows that the dynamic change of the roadbed is more balanced when the two-lane train is running,but the dynamic stress of the bed surface The change of the dynamic stress amplitude caused by the train load is larger than that of the single line.Therefore,the effect of the double line on the surface of the bed is more lasting and the damage is even greater.