An Analysis On Dynamic Response And Parameter Of The Slab Ballastless Track Of The High Speed Railway Subgrade

Tracing the process of the hundred year's development of the railway, the deadweight of the train has almost increased by ten times, and the speed has improved by more than then times. For keeping abreast of the new century and situation, the construction of the high speed railway has been placed on the schedule. Because the high speed railway has a higher speed (v>200km/h) and standard of the technology, higher standard for the aspects of design, construction and maintenance are requested, and the traditional conception on design has been improved and deepened, especially in the aspect of subgrade.Railway subgrade is the foundation that bears the track and train load. When choosing the reasonable stiffness and thickness, it can influence the distribution of the load obviously and the force on the surface of the track can decrease by 60%-70%. It also can improve the distribution of the dynamic stress in the subgrade bed. decrease the dynamic effect of the repeated load and the bad influence that the train load brings to the line. As the speed gets higher and the dynamic effect gets intensified, the dynamic response of the railway subgrade system becomes crucial. Choosing the reasonable model is the key to the study of the dynamic response of the ballastless track-subgrade system. The subgrade stretches along the longitudinally is relative large. When the train is coming, the probability of the exciting force that every beam sleeper supports is equal. And the simulation of the plane train load fully considers the influence of the exciting force on the nearby beam sleepers. So the situation that the subgrade under the train load and be dealt as plane strain question. Considering the typical section of the ballastless track subgrade, in this paper the finite element software ANSYS is used to build up a two-dimensional model on the basis of slab ballastless track and multi-tier system subgrade. And it chooses a reasonable train load and calculation parameters.Using the two-dimensional finite element model of the slab ballastless track and multi-tier system subgrade, in this paper, by studying the horizontal distribution of the vertical deformation, stress, strain and vertical acceleration at a certain section and time when the train load is exact acts on, the paper analyzes the dynamic response of the subgrade under the train load.Then by analyzing and comparing the influence according to the stiffness and thickness of the track slab and every layer of the subgrade, the paper gets the regulation that material parameters influence the dynamic response of the subgrade and find the main parameter that acts most. And it gives the basis of the dynamic optimization of the subguade.Then the conclusions are:(1)The subgrade bed is the most violent dynamic response area of the subgrade. So the rigidity of the subgrade bed is crucial for the stabilization of the subgrade. It is easiest to cause stress focus on marginal zone of the load-carrying board on the surface of the subgrade bed structure, leading to plastic deformation.(2)The increase of the rigidity of every layer of subgrade can decrease the vertical displacement of the structural tiers. And the rigidity of the ground is most effective for the subgrade. As the increase of the rigidity, the range of decrement becomes smaller. And exepting the surface of the subgrade bed structure, every layer of subgrade also can decrease dynamic stress on other tiers. But the dynamic stress increases in the changing tier of every layer of subgrade.(3)Exepting the surface of the subgrade bed structure,the increase of thickness of every layer of the subgrade can increase the vertical displacement in tiers which are above the changing tier. But the vertical displacement decreases in the tiers beneath the changing tier. And the increase of thickness of the surface of the subgrade bed structure can decreases the vertical displacement of the subgrade.The increase of thickness can also increase the dynamic stress in the changing tier and its upper tiers, but decrease that in below ones; when the thickness of the surface layer of the subgrade bed is 0.7m, the dynamic stress in the surface layer is minimal; when the thickness of the bottom layer of the subgrade bed is 2.0m, the dynamic stress of the bottom layer is minimal.(4)The change of the rigidity of every layer of the subgrade impact greatly on dynamic respond of the subgrade. The most positive factor is the ground rigidity, and the thickness impacts less. So the emphasis should be put on the rigidity rather than thickness.(5)The dynamics parameters which can influence the dynamic response of subgrade remarkably are the rigidity of the bottom layer of the subgrade bed,the rigidity of the subgrade embankment,the rigidity of the ground and the thickness of the surface of the subgrade bed.