Sealing system design and model testing of lining structures for artificial underground gas storage caverns in medium-hard rock strata

To better understand the in-service performance of the lining structural system in artificial underground gas storage facilities under repeated high-pressure cyclic loading, we conducted numerical simulations and physical model tests. The analyses accounted for long-term damage-induced deformation of the surrounding rock mass and examined the evolution of stress and deformation in an adaptable support system during cyclic pressurization. This study reveals the deformation and mechanical response characteristics of the lining structure during cyclic pressurization and depressurization in artificial underground gas storage, and verifies the feasibility of constructing underground gas storage caverns with thin steel linings in medium-hardness rock layers such as limestone and sandstone. The results indicate that the proposed adaptable support system design—comprising a 6 mm thin steel lining, wave-arch structures, rubber filling, and a secondary lining can achieve coordinated deformation with the surrounding rock and effectively transfer internal pressure under coupled cyclic loading. This system demonstrates the capacity to absorb high internal pressure and maintain sealing integrity. Under high internal pressure cyclic loading, the stress-strain time-history curves of the sealing steel lining and the circumferential reinforcement respond synergistically with the pressure curve, showing a stepwise increasing trend. Within the 0-6 MPa range, the strain of the steel lining increases rapidly with significant variation. Between 6 MPa and 10 MPa, the strain growth rate gradually decreases as the pressure rises. With an increasing number of cycles, the strain of the steel lining increases to varying degrees, but none exceed the yield strain of 2‰. Moreover, the stress in the outer-ring reinforcement of the secondary lining is consistently higher than that in the inner-ring reinforcement. Therefore, in future designs of underground gas storage, an asymmetric reinforcement design with larger-diameter outer-ring reinforcement could be adopted to enhance the overall load-bearing capacity of the lining. Additionally, the developed 15 MPa-level integrated water-air cyclic loading and unloading test and monitoring system for sealing structures in gas storage caverns will serve as a powerful tool for further analysis of artificial gas storage lining structures. The findings of this study provide fundamental experimental data and valuable references for subsequent key technologies in the construction of compressed air energy storage facilities in medium-hard rock formations.