Analysis Of Interlayer Shear Behavior Of Ballastless Track Based On Finite Element Model With Zero-Thickness Cohesion Element

Chinese high-speed railway has developed rapidly in the past decade.As an important track structure of high-speed railway,ballastless track has been widely used because of its good stability,strong integrity and durability.However,damage has occurred to the ballastless track successively under the continuous action of the complex environment.The relatively common one is the phenomenon of seams or even voids between the track slab and support layer,which affects the normal application of the track structure.In this thesis,double-layer concrete specimens were made to solve the problem of interlayer seams in the ballastless track.The finite element software was used to establish a meso finite element model to analyze the damage,displacement and stress of the interlayer interface.The main contents and results are as follows:(1)Based on the interlayer interface processing situation of the ballastless track in China,concrete composite specimens were made.Then the specimens were split by using the universal testing machine.The scanner was used to obtain the interlayer interface and to extract the contour lines every 10 mm.The slope root mean square method was used to calculate the interface roughness values for different interface treatments.The roughness values of the horizontal brushed interface,horizontal-longitudinal brushed interface and longitudinal brushed interface are 13.781,9.989 and 13.274 respectively.(2)In order to better observe the crack extension after the interlayer seams in the ballastless track occurred,a meso finite element model with the rough interface was established based on the extracted interface contour lines.Zero-thickness cohesive force units were inserted into the solid units in the model to simulate the bonding effect in concrete.(3)The effect of the vertical stress variation on the shear characteristics of the interlayer interface is analyzed by the meso finite method.Meantime,the relationship between the interlayer conformal ratio and stress increase range and the interlayer interfaces with different roughness is also analyzed by the same method.The roughness angles of four typical interfaces are obtained: 1.92° for the smooth interface,8.92° for the horizontal brushed interface,10.33° for the horizontal-longitudinal brushed interface,and 20.11° for the longitudinal brushed interface.