Abstract
Due to the fact that ballastless tracks in high-speed railways are not only subjected to repeated train–track dynamic interaction loads, but also suffer from complex environmental loads, the fundamental understanding of mechanical performance of ballastless tracks under sophisticated service conditions is an increasingly demanding and challenging issue in high-speed railway networks. This work aims to reveal the effect of train–track interaction and environment loads on the mechanical characteristic variation of ballastless tracks in high-speed railways, particularly focusing on the typical interface damage evolution between track layers. To this end, a finite element model of a double-block ballastless track involving the cohesive zone model for the track interface is first established to analyze the mechanical properties of the track interface under the loading–unloading processes of the negative temperature gradient load (TGL) followed by the same cycle of the positive TGL. Subsequently, the effect of wheel–rail longitudinal interactions on the nonlinear dynamic characteristics of the track interface is investigated by using a vehicle-slab track vertical-longitudinal coupled dynamics model. Finally, the influence of dynamic water pressure induced by vehicle dynamic load on the mechanical characteristics and damage evolution of the track interface is elucidated using a fluid–solid coupling method. Results show that the loading history of the positive and negative TGLs has a great impact on the nonlinear development and distribution of the track interface stress and damage; the interface damage could be induced by the wheel–rail longitudinal vibrations at a high vehicle running speed owing to the dynamic amplification effect caused by short wave irregularities; the vehicle dynamic load could produce considerable water pressure that presents nonlinear spatial–temporal characteristics at the track interface, which would lead to the interface failure under a certain condition due to the coupled dynamic effect of vehicle load and water pressure.
Highlights
With the advantages of strong stability, high smoothness and less maintenance, ballastless tracks for high-speed railways overcome the disadvantages of ballasted track, and have become the prior selection to enabling a rapid development of high-speed railways worldwide [1, 2]
The emergence and development of the interface damage will lead to the gradual destruction of the integrity of the track system; especially after the penetration of rain water, it will have a splitting and scouring effect on the track interface under train dynamic loads, which will intensify the expansion of the interface gap to the depth, and cause the ballastless track to gradually lose its bearing capacity, affecting the stability and durability of the track structure
The engineering practice has shown that the dynamic water pressure at track interface induced by vehicle dynamic loads may play an important role in the expansion of the interface cracks between ballastless track layers
Summary
With the advantages of strong stability, high smoothness and less maintenance, ballastless tracks for high-speed railways overcome the disadvantages of ballasted track, and have become the prior selection to enabling a rapid development of high-speed railways worldwide [1, 2]. Zhu et al were among the first that introduced the cohesive zone model to investigate the interface damage of slab tracks under temperature and vehicle dynamic loads [12], and further they obtained the damage constitutive model of the concrete interface of double-clock ballastless track based on experimental tests, with which the interface. Zhang et al [16] established a viscoelastic finite element model of a slab track incorporating viscoelastic parameters and a cohesive zone; the model was verified by experimental data and used to analyze the initiation mechanism of debonding under coupling actions of temperature and dynamic vehicle loadings. To reveal the mechanical characteristic variation and damage evolution at the track interface between track layers of ballastless tracks in high-speed railway, a cohesive zone model considering mixed-mode damage is employed to investigate the nonlinear mechanical characteristics and damage evolution of the track interface subject to complicated environment loads and vehicle-track interaction load. Some interesting and useful conclusions are drawn from the comprehensive numerical analysis, which may provide theoretical support for the maintenance strategy establishment and safe operation management of ballastless tracks in high-speed railways
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