Seismic safety of high-speed railway train track bridge systems: research progress, disaster mechanisms, and mitigation strategies

High-speed railway (HSR), as a rapid and efficient mode of transportation, is undergoing significant development in China. Bridge structures are widely utilized owing to their superior adaptability to terrain and rapid construction capability. However, as the HSR network expands into seismically active regions, it faces significant operational risks from sudden earthquakes. Earthquake induced line interruption and train derailment pose threats of severe economic losses and profound social impacts. Therefore, ensuring train running safety under seismic excitations and advancing disaster mitigation technologies are critical imperatives for the HSR construction and maintenance. This paper presents a systematic review of the state-of-the-art research about seismic safety of HSR train-track-bridge (TTB) coupling system. First, the numerical modelling methods and experimental test technologies for TTB coupling system are introduced. Next, disaster mechanisms of TTB coupling system under earthquake are analyzed, with a specific focus on train derailment. Then, the train running safety indices and safety evaluation methodologies are assessed. Subsequently, seismic resistance and vibration reduction strategies, alongside seismic response monitoring sensors are systematically summarized. Finally, the paper identifies key challenges and gaps to propose future research directions. This review aims to foster advancements in TTB seismic safety and enhance the resilience of HSR infrastructure against earthquake disasters.