Stress path and stability control of surrounding rock in caverns for compressed air energy storage

The stability of the compressed air energy storage (CAES) cavern is influenced by ground stresses during the construction phase and by cyclic high internal pressure (≥10 MPa) during the operational phase, resulting in different mechanical responses of the surrounding rock during the unloading and loading phases. This study investigates the stress paths of the CAES cavern from the perspectives of stress evolution and damage modes throughout both construction and operational phases. The findings indicate that during the excavation phase, active support technology significantly reduces deformation by adjusting the principal stress field of the surrounding rock, particularly in low-strength rock formations. Additionally, the load transfer effect decreases the burden on initial supports, such as steel arches. In the operational phase, the high internal pressure causes the sequence of principal rock stresses to shift, with radial stress increasing to the maximum principal stress and circumferential stress transitioning to the minimum principal stress. When exposed to hydrostatic pressure, characterized by low local stress and high rock strength, the surrounding rock at the tunnel wall may experience tensile failure during the high-pressure gas storage stage; otherwise, shear failure will occur at the tunnel wall. When the lateral pressure coefficient (λ) is less than 1, shear failure occurs in the surrounding rock at the side walls. In cases where the lateral pressure coefficient is particularly low, tensile failure may still happen at the arch crown. Conversely, when λ exceeds 1, shear failure is observed in the surrounding rock at the arch. If the lateral pressure coefficient is notably high, tensile failure may still occur at the side walls. As pressure increases, the area of tensile fractures may subsequently undergo shear failure. Further analysis reveals that conventional grouting and radial bolt systems significantly enhance stability only during the excavation phase. During operation, radial bolts not only lose their reinforcing capabilities but also exacerbate stress concentration in the surrounding rock under compression. In contrast, enhanced circumferential restraint effectively improves the stress state of the surrounding rock. For surrounding rock of good quality and high strength, grouting has limited efficacy in filling fractures. Conversely, grouting measures have been shown to increase the shear strength of formations characterized by low strength. Based on these insights, this study proposes an innovative solution for the stability control of CAES caverns subjected to complex stress paths by forming an anchor network system using crossed diagonal anchors and optimizing the inclination angle of the anchors to achieve a full-cycle tensile state.