Residual sealing performance of sealing materials under tensile cracking in linings of compressed air energy storage caverns

Underground shallow-buried compressed air energy storage (CAES) caverns are subjected to cyclic high-pressure loading during long-term operation, which may induce tensile cracking of concrete linings and consequently impair the integrity of sealing layers. However, the residual sealing performance and failure mechanisms of sealing materials under lining damage conditions remain insufficiently understood. In this study, a sealing performance evaluation framework integrating temperature effects, tensile cracking damage, and permeability evolution was proposed. Four typical polymer sealing materials, namely glass fiber reinforced plastic (GFRP), polyurethane, epoxy resin, and vinyl resin, were coupled with concrete linings to prepare composite specimens. Scanning electron microscopy (SEM), high-temperature treatment, Brazilian splitting tests, and gas permeability tests were conducted to investigate their mechanical behavior and residual sealing characteristics under different temperature and cracking conditions. The results indicate that increasing temperature mainly induces microstructural adjustments in the sealing materials, while some composite specimens maintain ultra-low permeability at temperatures below 100 °C, demonstrating favorable thermal adaptability. Among the investigated materials, epoxy resin exhibits the best residual sealing performance after tensile failure, with no through-going cracks observed and effective bonding with the concrete lining maintained. Furthermore, a two-dimensional radial gas seepage model was established to quantitatively evaluate cavern leakage under lining cracking conditions. The results show that, for lining cracking ratios ranging from 0.5% to 1.5%, the daily leakage rate of a cavern with an epoxy resin sealing layer is approximately 0.32%–0.95%. These findings reveal the damage-tolerant sealing mechanism of polymer sealing materials under lining cracking conditions and demonstrate the favorable applicability of epoxy resin for CAES cavern sealing. The results provide a theoretical basis for sealing material selection, leakage risk assessment, and the long-term safe operation of underground CAES caverns.