Stability analysis for compressed air energy storage cavern with initial excavation damage zone in an abandoned mining tunnel

Compressed air energy storage (CAES) is a buffer bank for unstable new energy sources and traditional power grids. The stability of a CAES cavern is a key issue to cavern safety. However, the stability of a cavern from an abandoned mining tunnel has not been well studied. This paper investigates the stability of the CAES cavern from an abandoned mining tunnel. Firstly, an initial heterogeneous excavation damage zone (EDZ) in the surrounding rock mass is partitioned based on mining and operation processes. Then, a thermal-hydraulic-mechanical coupling model is formulated for the CAES cavern with a sealing layer and implemented within COMSOL Multiphysics. After verification with available data in literature, this coupling model is used to investigate the influence of partitioned EDZ heterogeneity on the displacement and stability of cavern. It is found that the displacement at the cavern wall increases with operation cycle. The principal stress decreases with operation cycle in the high-damage zone but remains stable in the low-damage zone. The principal stress difference changes first and then becomes stable in the disturbance zone. Larger cavern radius, heat transfer coefficient, initial pressure of cavern, temperature of injected air, and faster gas injection rate induce bigger displacement. These results on the stability of a CAES cavern can be a basis for the repair of an existing cavern.