Mechanical performance of CRTS II slab tracks in reinforced-unreinforced transition zone in extreme heat events

Abstract

Anchors have been widely utilized to reinforce the CRTS II slab tracks. The mechanical performance of the tracks in the reinforced-unreinforced transition zone exposed to extreme heat waves can be very complex due to the difference in mechanical properties between the two kinds of track segments. This paper investigates the damage behavior of the tracks in the reinforced-unreinforced transition zone in extreme heat events. A finite element model of the CRTS II slab track in the transition zone has been established and validated, in which the nonlinear mechanical properties of track materials and interfaces are considered by applying the Concrete Damaged Plasticity model and the Cohesive Zone Model respectively. The nonlinear temperature field in the track structure in extreme heat events is applied to the model. Structural damage of the track, including slab-end arching and interfacial failure, in the transition zone under extreme heat is thoroughly investigated. In particular, the effects of joint use of post-installed reinforcement anchors and other track maintenance measures like interface adhesives and concrete joint restoration are studied. The following conclusions are drawn: (1) The more reinforced track-slabs in the transition zone, the milder the track diseases including slab-end arching and interfacial gapping. (2) Joint use of anchor installation and other maintenance measures such as interface adhesives and concrete joint restoration shows a better effect on mitigating track damage than using post-installed reinforcement anchors solely. (3) Concrete joint restoration overweighs interface adhesives in terms of reducing slab-end arching and interfacial damage when they are jointly used with post-installed reinforcement anchors. (4) In the transition zone, track damage surges when the air temperature increases from 42 ℃ to 47 ℃, which is the temperature range for an extreme heat wave. Monitoring of track state in the transition zones is necessary during extreme heat waves. The novel findings are expected to provide some insights into the mechanical performance of slab tracks and help to prevent potential damage to the tracks in the transition zone, which is a common and practical issue in railway engineering.