Study The Effects Of Complex Deformation On Ballastless Track System In Subgrade-Culvert Transition Section

Subgrade-culvert transition section is an important part of foundations of high speed railway. Materials, strength and stiffness of subgrade, transition section and culverts are different in subgrade-culvert transition section area, where complex deformations often occur. The complex deformations include different levels of subgrade settlement after the operation of railways, angle settlement in subgrade, transition section and culverts area, frost heave of subgrade in cold winter and different frost heave in subgrade, transition section and culverts area. These different forms of complex deformation can lead to track irregularity and gaps under base plates which will affect the steady and safety of train. Therefore, it is necessary to research the effect of subgrade complex deformation on track irregularity and gaps under base plates and dynamic response of vehicle-track system when train running at the high speed. This paper selects subgrade-culvert transition section of CRTSIII ballastless track as research subjects to analyze the static and dynamic response of vehicle-track structure caused by the subgrade complex settlement. The main research contents and results are as follows:(1) An entity statics model of ballastless track-subgrade culvert transition section is established in consideration of gaps between the base plate and the surface layer of subgrade. Research on force and displacement transfer relationship of subgrade-ballastless track-rail surface, irregularities characteristic of ballastless track, gaps between base plate and subgrade bed under the effects of complex deformation including cosine type settlement and angle type settlement of subgrade, culvert overall settlement, frost heaving of subgrade and different frost heaving of subgrade. And analyze the effect to the rail surface irregularities characteristic and gaps base on the actual monitoring data of frost heave. The calculation results show that with the deformation amplitude increases, the tensile stress of track structure is greater, the following of track structure becomes worse and the gaps between base plate and the surface layer of subgrade become bigger. With the wave length of deformation increases, the following of track structure becomes better and the gaps are smaller. Proposed limit for subgrade deformation can be determined based on gaps between base plate and surface layer of subgrade.(2) Considering 1:40 rail bottom slope and multi point elastic support fasteners and using the viscoelastic dynamic artificial boundary, a refinement and large scal vehicle-ballastless track-subgrade-transition section dynamic model is established based on the vehicle-track-subgrade coupling dynamics. Study on the dynamic responses of vehicle-track system under the complex deformation including cosine type settlement and angle type settlement of subgrade, culvert overall settlement, frost heaving of subgrade and different frost heaving of subgrade. The calculation results show that with the deformation amplitude increases, the dynamic effects on vehicle and track structure are greater. Deformation amplitude has a significant effect on vertical acceleration of car body and vertical force of the wheel/rail, but has little effect on lateral acceleration of car body. The proposed limit of complex deformation is obtained under the consideration of vehicle safety and passenger comfort of vehicle-track dynamic security index based on the dynamic calculation results.(3) According to the results of static and dynamic calculation, the control limit value of cosine type uneven settlement of subgrade in front of culvert transition should be within 10mm/20m and control limit value of angle type uneven settlement of subgrade in front of culvert transition should be within 1‰. The control limit value of cosine type uneven settlement of subgrade in culvert transition should be within 10mm/20m and control limit value of angle type uneven settlement of subgrade in culvert transition should be within 1‰. The control limit value of overall settlement of culvert should be within 2mm. The frost heave of subgrade should be limit within 10mm/20m. The maximum dynamic responses of vehicle-track system under the actual monitoring frost heave data are less than security index of vehicle-track dynamics. It shows that the train can pass through subgrade-culvert transition section at the speed of 350km/h without speed limit.