Objective Gravity Compressed Air Energy Storage (G-CAES) offers advantages of large-scale, long-duration energy storage and flexible regulation. As a key underground structure, the vertical-shaft gas storage cavern must withstand cyclic internal pressure, temperature fluctuations, and sealing constraints during operation. To clarify temperature variations, structural stresses, and surrounding rock response mechanisms during cyclic charging and discharging, this study focuses on vertical-shaft gas storage caverns with a gradually enlarged lower section. By considering the multi-material coupling among the sealing steel liner, concrete lining, and surrounding rock, the study reveals the mechanical evolution law of the structural system of the vertical-shaft gas storage cavern under thermo-mechanical coupling.

Methods A three-dimensional finite element model of “sealing steel liner-concrete lining-surrounding rock” is established. The thermo-mechanical coupling numerical method is adopted to simulate cyclic operating processes including gas charging, gas storage and gas discharging. Spatiotemporal evolution characteristics of temperature field, stress field and displacement field are analyzed. Differences in near-wall heat accumulation and structural response under single-cycle and multi-cycle actions are compared, and load-controlling factors for key positions are further identified.

Results (1) Near-wall temperatures exhibit a distinct three-stage “rise–slow rise–drop” pattern across the gas-charging, storage, and discharging stages, respectively. By the end of the fifth cycle’s charging and storage stages, peak temperatures reach approximately 30.7 °C at the steel liner inner wall and 30.2 °C at the concrete lining inner wall. Thermal disturbance is largely restricted to the sealing steel liner and the adjacent 1 m zone of concrete lining, with minimal response from the deep surrounding rock. (2) By the end of the fifth cycle’s charging and storage stages, the sealing steel liner experiences peak tensile and compressive stresses of approximately 9.90 MPa and −55.31 MPa, indicating a sufficient overall strength margin. Meanwhile, maximum tensile and compressive stresses in the concrete lining reach approximately 1.92 MPa and −3.49 MPa; however, localized tensile stresses near the shaft wall–bottom transition warrant further crack-resistance evaluation. (3) The radial displacement of the steel liner exhibits a “large in the middle and small at both ends” pattern, whereas the concrete lining undergoes outward bulging along its inner wall and inward contraction along its outer wall. While cumulative cyclic temperature rise drives a slow evolution of principal stresses and displacements in both the steel liner and concrete lining, the response of the surrounding rock remains minimal.

Conclusion Under cyclic operation, the vertical-shaft gas storage cavern with a gradually enlarged lower section maintains overall mechanical stability. Thermo-mechanical coupling primarily affects near-wall structural zones and local transition regions. These findings provide references for thermal management, targeted reinforcement, interface-structure optimization, and operational strategies for G-CAES facilities, and offer a basis for subsequent field-monitoring layout and long-term service-performance evaluation.