Optimized joint repair effects on damage evolution and arching mechanism of CRTS II slab track under extreme thermal conditions

• 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.