Interfacial Properties of Double-Block Ballastless Track under Various Environmental Conditions

The natural environment has a great effect on the interfacial bonding performance of ballastless track in highspeed railways, and the interfacial damage analysis models of the double-block ballastless track (DBBT) on subgrade with two connections and four interface conditions are proposed in this paper. Firstly, the cohesive zone models (CZM) parameters of two interfaces of the DBBT were calculated and the thermal responses of a 1/4 scaled DBBT in an outdoor natural environment were measured. After the validation of outdoor experimental results, the transient heat transfer models of the unitized and longitudinal DBBT with four interfacial CZMs were then established to study their interfacial damage properties under three elevated temperatures, respectively. Thermal responses of the unitized and longitudinal DBBT are also compared under the coupling effect of high temperature and humidity. Results show that the temperature and longitudinal stress generally decrease from the sleeper to the supporting layer in a natural environment. The CZM has a great effect on interfacial thermal responses, and the stresses of the track slab in the longitudinal DBBT are much larger than those of the unitized DBBT under three elevated temperatures. More importantly, the damage factors of the two interfaces of the unitized DBBT are much larger than those of the longitudinal DBBT, and the interfacial damage development of the two interfaces of the unitized DBBT is different from the longitudinal DBBT. In addition, the coupling effect of a high temperature and humidity could effectively increase the thermal responses of the track slab for two DBBTs, especially for the higher humidity that exceeds RH=65 % of the unitized DBBT.