Implementing compressed air energy storage (CAES) in lined caverns provides a promising technical solution for large-scale energy storage, and the reasonable selection of sealing materials is essential for its success. Flexible membrane materials including sprayable polymers, rubber sheets, and airbags have recently been considered economical and practical sealing options. However, research on flexible membrane sealed CAES caverns remains limited, particularly regarding their mechanical response and parameter sensitivities. To address this gap, an elastic multilayer thick-walled cylinder model verified by physical model tests is proposed. Analytical solutions for the stress and displacement fields of the surrounding rock and concrete lining are derived, and a calculation scheme is designed to evaluate the influence and sensitivity of key parameters. Results indicate that under high internal pressure, both the lining and surrounding rock undergo radial compression without yielding, whereas the lining experiences adverse tensile stresses in the hoop direction. The maximum hoop tensile stress reached the order of 1~3 MPa under typical CAES operating pressures, and tensile-compressive stress transformation may occur in the lining under certain parameter combinations. Sensitivity analysis further shows that internal pressure, in situ stress, surrounding rock elastic modulus, and cavern radius are the dominant factors influencing the mechanical behavior of the system, while geometric and lining parameters have secondary but non-negligible effects. The findings provide theoretical support for the stability analysis and material design of flexible membrane sealed CAES caverns and offer useful guidance for determining allowable operating pressures and selecting lining configurations.

Understanding the failure mechanism of soft rock roadways in high-humidity environments, as well as designing appropriate control measures, are critical for ensuring their stability. In this study, swelling and triaxial compression tests on argillaceous sandstone were first performed. Results show that the triaxial compressive strength (TCS), elastic modulus, cohesion, and internal friction angle of argillaceous sandstone are all decreased due to the water weakening effect. Then, a self-developed finite-element-based numerical code was employed to elucidate the role of humidity diffusion in the deformation and failure of soft rock roadways. Simulation results indicate that under the influence of humidity, high stress concentration zones develop, initiating microcracks within these regions. As humidity continues to diffuse, the high stress concentration zones expand and migrate deeper into the surrounding rock, causing microcracks to propagate and accelerating humidity diffusion. This cyclical process repeats, ultimately resulting in macroscopic fracturing. The failure of roadway exhibits a tensile–shear mixed mode during humidity diffusion. A comparative analysis of four control measures reveals that conventional non-waterproof shotcrete primary support is of limited effectiveness in ensuring the stability of high-humidity soft rock roadways. It is essential to promptly establish a closed waterproof support structure. Furthermore, localized support defects significantly impact control effectiveness.

Water significantly modifies rock mechanical performance and fracture characteristics through water content and water distribution. Nevertheless, the evolution laws of rock mechanical properties and underlying fracture mechanisms under variable water conditions remain incompletely clarified. In this study, uniaxial compression tests were carried out on sandstone samples with diverse water immersion durations. Experimental observations reveal that the uniaxial compressive strength (UCS) and elastic modulus of sandstone follow negative exponential attenuation with prolonged immersion time, with maximum reductions of 50.1% and 25.6%, respectively. Under equivalent water contents, samples featuring dry exteriors and wet interiors possess lower strength than those with wet exteriors and dry interiors. A self-developed numerical code incorporating humidity diffusion effects was subsequently adopted to interpret water-controlled sandstone fracture behaviors. Numerical outputs verify that water-induced softening and heterogeneous water distribution exacerbate rock material heterogeneity and internal stress non-uniformity, triggering tensile microcracks along dry–wet interfaces. As the immersion duration rises, the rock failure mode transitions from shear-dominated mixed failure to tension-dominated failure, and finally reverts to shear-dominated mixed failure. Macroscopic rupture is predominantly governed by the gradual coalescence of tension-generated microcracks. This study offers a theoretical foundation to advance the understanding of water-triggered mechanical degradation and fracture mechanisms in sandstone.