Key Takeaways & Executive Findings
- •• Optimized joint repair increases the initial damage temperature of the CRTS II slab track by 11°C, significantly delaying thermal-induced damage. • Under the most unfavorable heating load with temperature gradient, joint repair reduces the maximum stiffness degradation index (SDEG) by approximately 81.16%. • Repairing joints reduces upward arching deformation by 93.96%, greatly improving slab track stability under extreme thermal conditions. • Even after repair, interface shear strength damage can still cause the track arch to increase by 2.616 mm, highlighting the need for interface maintenance.
Abstract
To address the issue of extreme thermal-induced arching in CRTS II slab tracks due to joint damage, an optimized joint repair model was proposed. First, the formula for calculating the safe temperature rise of the track was derived based on the principle of stationary potential energy. Considering interlayer evolution and structural crack propagation, an optimized joint repair model for the track was established and validated. Subsequently, the impact of joint repair on track damage and arch stability under extreme temperatures was studied, and a comprehensive evaluation of the feasibility of joint repair and the evolution of damage after repair was conducted. The results show that after the joint repair, the temperature rise of the initial damage of the track structure can be increased by 11 ℃. Under the most unfavorable heating load with a superimposed temperature gradient, the maximum stiffness degradation index SDEG in the track structure is reduced by about 81.16% following joint repair. The joint repair process could effectively reduce the deformation of the slab arching under high temperatures, resulting in a reduction of 93.96% in upward arching deformation. After repair, with the damage to interfacing shear strength, the track arch increases by 2.616 mm.
1. Introduction
The slab track is one of the primary track structure forms for high-speed railways globally, distinguished by its exceptional advantages. The China Railway Track System (CRTS) II slab track holds a significant share in China’s high-speed railway network, with a total operational mileage of approximately 8800 km. CRTS II slab track is constructed of prefabricated slabs connected longitudinally by joints. The joint concrete structure is complex, construction quality is difficult to control, and it is greatly affected by periodic effects such as high and low temperatures and train load.
According to on-site statistics, several systemic issues were found on the longitudinal track structure of a certain railway, with the maximum height difference being a minor deviation. Most issues along the track are related to joint damage. Under extreme and repeated rising and cooling conditions, it first causes great damage to the weak structure of the track, which is manifested as joint damage. In the worst-case scenario, this instability can lead to considerable compromise in the integrity of the longitudinal connection system, adversely affecting the stability and durability of the track structure, ultimately posing a risk to the safety of train operations.
The CRTS II slab track consists of, from top to bottom, rail, fasteners, prefabricated slab, cement asphalt mortar (CA mortar) layer, and concrete base. The slab is a precast plate connected to the longitudinal continuous structure via the joint between precast slabs. Due to its longitudinal continuous structural characteristics, issues such as arch separation and wide joint damage may arise in isolated weak sections during extremely high temperature conditions. Field investigation shows that the lower part of the joint concrete can be damaged and crushed, with interface cracking and transverse penetration failure between track layers, and a trend of expansion in the longitudinal direction.
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CAI Xiao-pei, CHEN Ze-lin, CHEN Bo-jing, ZHONG Yang-long, ZHOU Rui, HUANG Yi-chen (2025). Optimized joint repair effects on damage evolution and arching mechanism of CRTS II slab track under extreme thermal conditions. Journal of Central South University. https://doi.org/10.1007/s11771-025-5988-1
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Frequently Asked Questions
What is the CRTS II slab track?
The CRTS II slab track is a longitudinal continuous track structure used in China's high-speed railways. It consists of prefabricated concrete slabs connected by joints, with a cement asphalt mortar layer and a concrete base. It is susceptible to joint damage and arching under extreme thermal conditions.
Why is joint repair important for CRTS II slab track?
Joint repair addresses the weak joint areas where thermal-induced damage initiates. By repairing joints, the track can withstand higher temperature rises before initial damage, reducing the risk of arching and preserving the structural integrity and safety of the high-speed railway.
What improvements were observed after optimized joint repair?
After optimized joint repair, the temperature rise for initial damage increased by 11°C, the maximum stiffness degradation index (SDEG) reduced by about 81.16%, and upward arching deformation decreased by 93.96% under severe heating conditions.
Does joint repair completely eliminate arching risk?
No. Even after joint repair, damage to interface shear strength can still lead to an arch increase of 2.616 mm. This indicates that interface conditions also require monitoring and maintenance to fully ensure long-term stability.
What methods were used in this study?
The study derived a formula for safe temperature rise using the principle of stationary potential energy. Considering interlayer evolution and structural crack propagation, an optimized joint repair model was established and validated, followed by numerical analysis of damage and arching behavior.
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