Numerical Analysis and Safety Assessment of Dynamic Response of Natural Gas Pipelines Under Vibration Loads from High-Speed Railway Tunnels

With the rapid expansion of high-speed railway (HSR) networks, the vibration impact on adjacent energy infrastructure has become a critical safety concern. However, existing research lacks a comprehensive evaluation of buried sour gas pipelines specifically in tunnel-undercrossing scenarios. This research investigates the dynamic response characteristics of a sour natural gas pipeline under train-induced vibration loads using a case study in Chongqing. A three-dimensional dynamic coupling model of the track lining soil pipeline system was established based on FLAC-3D. The study innovatively quantifies the vibration superposition effect during bidirectional train encounters and assesses safety using fatigue life and velocity thresholds. Results indicate that pipeline vibration is predominantly vertical. As train speed increases from 250 km/h to 350 km/h, the response exhibits a non-linear rapid growth within the 300–350 km/h range. Under bidirectional encounters, the peak displacement reaches 2.00 times that of unilateral passage, representing the most critical load condition. The maximum peak vibration velocity is 0.1 mm/s, far below the 2 mm/s safety threshold, ensuring structural integrity under current operational standards.