# Evolution Mechanism of Interlayer Properties of CRTS III Slab Track during Construction
## 1 Introduction
[19] introduced the CZM to build the CRTS II slab track model and studied the effect of temperature on the damage and deformation of the interface between the track slab and CA mortar. [PERSON] et al. [20] accurately simulated the interfacial debonding process of a longitudinal continuous slab track by combining on-site experiments, finite element analysis, and machine learning methods. [PERSON] et al. [21] studied the effect of different temperatures and constraint conditions on the interfacial bonding properties of track slab-CA mortar. [PERSON] et al. [22] proposed a method for accurately evaluating the time-varying reliability of interlayer damage in slab tracks. In addition, some scholars have conducted relevant research on the finite element modeling method of concrete fracture mechanics. [PERSON] et al. [23] studied the corrosion effects on the capacity and conductivity of concrete half-joint bridges using the finite element method. [PERSON] et al. [24] proposed a method for calculating the virtual crack propagation length based on experimental data and constructed a fracture analysis model for studying the parameter discreteness of roller compacted concrete materials. From the above research, it can be seen that the CZM, as a constitutive relationship that expresses the evolution of interlayer characteristics, can accurately reflect the evolution process of interlayer damage in slab tracks. Furthermore, for the CRTS III slab track, the hydration heat after pouring SCC will directly lead to the rapid evolution of the temperature field of the track structure. Therefore, it is crucial to accurately obtain the temperature field of the slab track structure. [PERSON] et al. [3] built a thermodynamic model for the CRTS III slab track, analyzing the temperature field of the track structure under solar radiation and environmental temperature conditions. [PERSON] et al. [25] conducted full-scale temperature field tests on the CRTS III slab track and obtained its temperature variation characteristics in the natural environment. [PERSON] et al. [16], [PERSON] et al. [26], and [PERSON] et al. [27] analyzed the temperature field and thermal effects of a longitudinally connected slab track under typical climate conditions in Beijing through on-site testing and thermodynamic model simulation methods, respectively. In summary, there are relatively few studies that focus on the interface damage of CRTS III slab tracks during construction. Meanwhile, it should be noted that the constitutive parameters of the new-old concrete interface are theoretically time-varying with the increase in SCC age. In addition, the Young's modulus, shrinkage load, and heat of cement hydration of the SCC are constantly changing during the construction phase. However, the existing constitutive models and finite element models of the CRTS III slab track pay less attention to this point. In this paper, taking into account the time-varying parameters of the interface constitutive model between track slab and SCC, a novel multi-field coupled FEM of the CRTS III slab track under construction was established, based on which the interface damage evolution law and its influencing factors were investigated. Specifically, based on the evolution data of strength, stiffness, and fracture energy of new-old concrete with age, an interface time-varying coefficient was proposed, and a bilinear CZM was improved. A multi-field coupled finite element model for the evolution of interlayer damage to the CRTS III slab track during construction was established and validated. The evolution mechanism of interlayer damage to slab tracks during construction was revealed, and the mechanical response of track structures after interlayer damage was analyzed. The influence of key parameters such as interfacial bonding strength, shrinkage of SCC, and environmental temperature on the interlayer characteristics of slab tracks during early construction was discussed. This provides a theoretical reference for effectively controlling the interlayer gap of the slab track during construction.