Parametric Modeling Method And Dynamic Response Analysis Of CRTSⅢ Slab Ballastless Track-Subgrade System

With the rapid development of high-speed railway in China,the design and construction technology of CRTS III ballastless track has been gradually improved.As the foundation for bearing train load,the soil structure of the subgrade is in a complex stress environment under the action of moving train load.Based on this,by reviewing a large amount of literature and relevant specifications,this paper uses the finite element software ABAQUS as the calculation and secondary development platform.A CRTS III slab ballastless track-subgrade-foundation finite element model is built,used to analyze the vertical dynamic response of the subgrade structure under the action of moving train load.The main research work is as bellow:(1)Considering the effects of train static load,geometric irregularities and additional dynamic load,the expression of wheel-rail excitation force function is improved,and Fortran language is used to write the moving load subroutine for 250km/h,300km/h,350km/h and400km/h.Based on the secondary development of finite element software,the ballastless tracksubgrade system parametric modeling plug-in is built.The numerical calculation results are compared with the measured data,and the results show that the vertical dynamic stress amplitude variation on the subgrade surface is consistent with the measured data.The measured vertical dynamic stress variation range is 8.4～14.5k Pa,and the numerical calculation result of this paper is 12.2k Pa.(2)Using the numerical calculation method,the vertical dynamic response of the subgrade structure under the action of moving train load is calculated by the CRTS III slab ballastless track-subgrade-foundation finite element model.The vertical dynamic displacement is uniformly distributed among the subgrade surface,reflecting the advantage of good integrity of the slab ballastless track.The influence of structural and loading parameters on the vertical dynamic response of ballastless track-subgrade system is also analyzed,and the "decay of unit modulus of subgrade surface" is proposed to compare the relationship between the smoothness of subgrade surface and the elastic modulus of each structure,which provides data supported for the optimal design of subgrade structure.(3)A finite element model applicable to the temperature gradient is built,which analyzes the deformation characteristics of ballastless track-subgrade under the action of moving train load and temperature gradient.The results show that the track plate occurs obvious upward arch and buckling deformation respectively under the effect of positive and negative temperature gradient,and causes the same trend of deformation on the surface of subgrade.Under the combined load,the train load is the main factor causing vertical displacement of ballastless track-subgrade structure.The track plate still maintains the characteristic deformation caused by internal temperature gradient,which affects the magnitude of displacement on the surface of subgrade.Therefore,in the area with large temperature difference between day and night,the influence of internal temperature stress of track plate must be paid attention to.