Failure mechanisms of underground compressed air energy storage caverns under ultimate air-storage conditions: Insights from physical model testing and numerical analysis

This study investigates the failure mechanisms of underground compressed air energy storage (CAES) caverns under ultimate air-storage conditions through an integrated approach combining large-scale physical model testing and thermo-mechanically coupled phase-field simulations. The physical model tests reveal that underground CAES caverns predominantly exhibit tensile-dominated brittle failure, with deformation evolving from an initial linear elastic response to nonlinear damage accumulation before catastrophic structural instability occurs. The developed phase-field framework successfully reproduces the experimentally observed fracture initiation and propagation processes, demonstrating its capability for predicting the ultimate failure behavior of underground CAES caverns. The results further demonstrate that in-situ stress conditions significantly enhance the ultimate pressure-bearing capacity of underground CAES caverns, while the lateral pressure coefficient governs both fracture morphology and propagation direction. Comparative analyses of different lining systems indicate that reinforced concrete markedly improves the load-bearing capacity and crack resistance of underground caverns, whereas flexible concrete effectively suppresses lining damage and enhances overall structural integrity. These findings provide new insights into the ultimate failure mechanisms of underground CAES caverns and offer important theoretical guidance for anti-cracking design, lining optimization, and the safe development of underground compressed air energy storage systems.