Preliminary Study On Interface Performance For Longitudinal Ballastless Track In High-speed Railway Bridges

Longitudinal ballastless track system (China Railway Track Slab II) was widely used in China’s high speed ballastless railway system. The total mileage in double line has reached to4415km until2014. Depending on its good binding capacity with the interface of track slab and bed plate, CA mortar transmitted the longitudinal, transverse and vertical forces, provided constraints resistance for the track slab as well. A section of6.45m long (the standard track slab length) track-CA mortar-bed plate structure of the ballastless track system on bridges was intercepted as a research object. By finite element calculations and field tests, the mechanism of interface load transfer was explored. The main contents of this paper included:1. Regard track slab, CA mortar and bed plate equivalent to three glued composite material structures, the conception of’laminated beam’was proposed. Based on the basic theory of laminated beam, the load transfer pattern of CA mortar was expounded and the shear interfacial stress formula of CA mortar was deduced.2. According to different constraint assumptions between mortar and track slab,3kinds of finite element model (FEM) were established, the interface’s working performance of ballastless track system was analyzed comprehensively under various conditions, the correctness of these models were also confirmed. The interface coupling FEM applied to the condition when there was entirely no relative displacement between track slab and mortar interface. By assuming the nonlinear relationship of cohesive force and displacement along the longitudinal, vertical and transverse direction, calculation results of the interface nonlinear FEM were closer to the actual working state of the mortar layer interface. Besides, the working state of the system after the interface was destroyed completely was reflected by the interface sliding FEM.3. On the basis of interface nonlinear models, the influences of shear strength, cohesion strength, the strength relationship between the mortar’s upper and lower interfaces to the constraint forces and ultimate anti-shear capacity of mortar interface were investigated through parameter analysis. 4. Combined with the actual construction of the longitudinal ballastless track system’s mortar layer, the field testing and numerical simulation were carried out. And the influence of residual mortar in fill orifice to the interface’s longitudinal and transverse anti-shear capacity were analyzed in detail when the cohesive force of the mortar were lost.