Abstract: High internal pressure can readily cause cracking in the underground cavern of compressed air energy storage (CAES), posing a significant threat to its stability and sealing. To effectively transfer internal pressure loads, enhance cavern deformation capacity, and leverage the bearing capacity of surrounding rock, we propose a flexible lining design using low-elastic modulus flexible concrete as the lining layer for CAES underground caverns. The mechanical properties of flexible concrete under various proportions are initially investigated through laboratory tests. Building on these findings, we propose a modified concrete damage-plasticity (CDP) constitutive model for flexible concrete and establish a mechanical calculation model for underground caverns utilizing flexible concrete. To demonstrate the feasibility of using flexible concrete in CAES underground caverns, this study compares the mechanical response of these caverns with different lining forms and varying flexible concrete ratios. This comparison is conducted within the context of an ongoing CAES underground cavern project. The results indicate that low-elastic modulus flexible concrete can effectively reduce tensile stress in the concrete lining of high-pressure CAES underground caverns. This stress reduction minimizes lining cracking, facilitates internal pressure load transfer, enhances cavern deformation capacity, and leverages the bearing capacity of surrounding rock.

Key words: compressed air energy storage (CAES), flexible concrete, underground cavern, stability