Brittle and Fatigue damage behavior of surrounding rock masses in CAES cavern under cyclic thermos-mechanical coupled loading

A coupled thermo-hydro-mechanical-damage (THMD) model is developed to investigate the brittle and fatigue damage behavior of surrounding rock in compressed air energy storage (CAES) cavern under cyclic thermos-mechanical coupled loading. Material heterogeneity is explicitly considered using a Weibull distribution. The effects of lateral pressure coefficient, cavern cross-sectional shape, and cyclic internal pressure on brittle and fatigue damage evolution are systematically examined. Results show that the total damage accumulation is minimized when the lateral pressure coefficient approaches unity, where the stress distribution is more uniform. Deviation from unity enlarges the damaged zone, with K h = 1.5 causing significantly greater fatigue damage than K h = 1.2. Cavern shape dictates crack initiation sites and overall fatigue damage patterns. Under cyclic pressurization, the fatigue damaged zones progressively expand with each cycle, and adjacent cracks gradually coalesce. The proposed model reliably captures both tensile and shear fatigue damage modes, providing a theoretical basis for differentiated support design in CAES cavern under repeated loading conditions.