Objective Compressed air energy storage (CAES) in a lined hard rock cavern holds great prospects. However, the load sharing mechanisms of the cavern’s composite structure, comprising a sealing layer, lining, and surrounding rocks, remain poorly understood.

Methods Based on the elastic analytical solutions of stress fields, this first study derived the radial load equilibrium equations for the composite structure of a lined hard rock cavern for CAES. Accordingly, a novel method for calculating the load sharing ratios of the composite structure was developed. Then, an analysis scheme for the load sharing ratios was designed. Using this scheme, this study investigated the variation patterns of the load sharing ratios of the composite structure under the influence of different factors. Finally, key factors influencing the load sharing ratios were determined through parameter sensitivity analysis.

Results and Conclusions  The results indicate that in the composite structure of a lined hard rock cavern for CAES, surrounding rocks represent the primary bearer of the high pressure load for gas storage (80%‒90%). In contrast, the sealing layer shares a small proportion of the load (1%5%), while the load sharing ratio of the concrete lining is significantly affected by design parameters, varying from 5% to 20% under the proposed parameter combinations. The load sharing ratios of various structural layers exhibit nonlinear relationships with the cavern radius, the elastic modulus of surrounding rocks, and the gas storage pressure, while showing approximately linear relationships with other parameters. In terms of parameter sensitivity, the elastic modulus of surrounding rocks exerts the most significant influence on the load sharing ratios of the composite structure, followed by the elastic modulus of concrete lining, gas storage pressure, cavern radius, lining thickness, in situ stress, and thickness of the steel sealing layer sequentially. The joint load bearing design for the composite structure should account for the load sharing function of the lining. Appropriately increasing the lining thickness can effectively increase the load sharing ratio of the lining while also improving the circumferential tensile stress conditions of the composite structure. In contrast, raising the concrete grade, despite slightly increasing the lining’s load sharing ratio, tends to increase the circumferential tensile stress, thereby increasing the risk of lining cracking. The results of this study can provide certain theoretical guidance for gaining insights into the load-bearing mechanisms and optimizing the design of the composite structure of a lined hard rock cavern for CAES.