Research on influence patterns of fault activation on lining structures in lined rock caverns for underground hydrogen energy storage

Underground hydrogen energy storage (UHES) in lined rock caverns (LRCs) is a promising solution for mitigating the instability of clean energy generation. However, the hydrogen injection/extraction process may activate potential faults surrounding the caverns, jeopardizing the service safety of the lining structures. In this study, a novel polymeric sealing layer was developed and tested for UHES, to replace the traditional steel lining. A numerical model of fault activation was established to analyze the mechanical response of the lining structures under various parameters, such as injection/extraction operation parameters, fault characteristics, and concrete lining forms. Results show that the stress level of the concrete lining is directly related to the number of hydrogen injection/extraction cycles, fault angle, and magnitude, while it diminishes with increasing fault distance. The flexible joint fillers could disperse the circumferential stress and absorb energy continuously during fault activation, resulting in lower stress levels and damage to segmental concrete lining, compared with integral concrete lining. The sealing layer, protected by the concrete lining, experiences lower stress fluctuations during fault activation. Additionally, the results obtained show that a certain distance threshold for fault-induced damage to the concrete lining was identified, beyond which fault activation no longer triggers damage. The distance threshold was tentatively determined to be 20 m.