Surface subsidence induced by salt cavern gas storage and its impact on railway safety: Numerical simulation and fuzzy evaluation

• A 3D geomechanical numerical model was developed to simulate pressure response in salt caverns. • An optimized pressure range was proposed based on minimum principal stress and steady-state creep. • A multi-indicator safety evaluation system was established for quantitative risk classification. • Surface subsidence and its impact on railway subgrade stability were quantitatively evaluated. • The study provides a safety management framework for gas storage and infrastructure protection. Salt cavern gas storage plays a vital role in energy security; however, its operation can induce surface subsidence, which poses a threat to nearby railway subgrades. This study focuses on the Jintan T gas storage facility. Using FLAC-3D for numerical simulation, we analyze the long-term contraction, deformation, and subsidence of the salt cavern. The results reveal that factors such as changes in cavern formation volume, the rheology of salt rock, and pressure fluctuations during gas injection and withdrawal significantly influence these processes. We propose a safety assessment framework based on the Analytic Hierarchy Process (AHP), which takes into account various factors, including cavern subsidence, train operation parameters (axle load, speed), subgrade conditions (lithology, fill characteristics), and subgrade protection measures (e.g., retaining structures and slope stabilization). A fuzzy comprehensive evaluation is subsequently performed. The findings suggest that optimizing the operating pressure of the gas storage chamber and reinforcing subgrade protection measures can enhance the safety of railway embankments. This research provides engineering guidance for improving the safety of railway infrastructure near salt cavern gas storage facilities and offers practical insights for optimizing the design and operation of underground energy storage systems.