Abstract: The surrounding rock mass serves as the primary load-bearing structure in underground CAES caverns, making its stress and deformation behaviour during the charging and discharging process critically significant. Nevertheless, the theoretical framework for elastoplastic deformation of the surrounding rock mass under long-term cyclic expansion dynamic loading remains poorly understood, and the stress paths of the whole process from excavation to cyclic charging and discharging operations are not clear. Accordingly, based on the stress characteristics of the CAES caverns, an analytical solution for elastoplastic deformation of surrounding rock mass throughout the excavation and operational phases is proposed in this study. The reliability of the proposed solution is verified by comparing with the numerical simulation results of commercial software FLAC3D. Furthermore, a parametric sensitivity analysis is conducted using a fixed computational scheme. The analysis evaluates how geological conditions and operational parameters influence the mechanical response of the surrounding rock mass. The main conclusions are as follows: (1) The mechanism that surrounding rock mass will not continue to expand outward is clarified. Under the set working conditions, surrounding rock mass mainly exhibits plastic cumulative deformation inward, resolving the long-standing issue of CAES caverns expansion that has plagued engineering practice. (2) The evolution of the stress path in the surrounding rock mass from excavation through operation is revealed, and the stress path remains between the high- and low-pressure yield lines throughout this period. (3) A method for determining the elastic operating pressure range of the surrounding rock mass of the CAES caverns is developed. This range depends on cohesion and internal friction angle. Operating within this range ensures the surrounding rock mass remains in an elastic state without plastic deformation, thereby addressing a theoretical gap in CAES caverns operating pressure range theory. (4) It is clear that the deformation of surrounding rock mass is most significantly influenced by the minimum and maximum gas storage pressures, while the frequency of charging-discharging also plays an important role. These findings provide theoretical support for the design and construction of CAES power plants.

Key words: compressed air energy storage, surrounding rock mass, stress path, expansion, operating pressure range