Coupled thermo-mechanical simulation of lining cracking evolution and sealing system mechanical response in CAES lined rock caverns using finite-discrete element method

• Developed a coupled thermo-mechanical FDEM framework for fracture analysis of CAES lined rock caverns. • Quantified crack width, porosity evolution, and steel liner stress under coupled temperature–pressure loading. • Clarified the roles of temperature, rock stiffness and lining design parameters in crack control and sealing performance. Lined rock caverns (LRCs) have become a key underground solution for large-scale compressed air energy storage (CAES). Clarifying the lining’s cracking pattern is a prerequisite for achieving coordinated performance with the sealing layer. This study proposes a coupled thermo-mechanical numerical framework based on the finite-discrete element method, which can effectively predict the random cracking process and crack evolution patterns of the lining. The accuracy and applicability of the proposed framework are verified through comparison with results from laboratory model tests. Finally, an engineering-scale model is constructed to investigate the effects of factors such as thermal effects, surrounding rock stiffness, and reinforcement parameters on the cracking characteristics and mechanical performance of the lining-sealing system. Results show that thermally induced circumferential compression offsets tensile stresses caused by internal pressure, reducing the maximum crack width and the steel liner stress amplitude by approximately 30%. Surrounding rock stiffness governs deformation compatibility: a higher elastic modulus suppresses plastic zone expansion, significantly reduces cracking, and improves the stress uniformity of the steel liner. Reinforcement factors (including reinforcement type, bar diameter, and spacing) have a limited effect on crack development and overall stress in the steel liner but influence the uniformity of stress in the sealing layer. Lining thickness exhibits a dual effect: thicker linings generate fewer but wider cracks, whereas thinner linings produce more but narrower cracks. The proposed framework provides a reliable theoretical and engineering basis for safety assessment and design optimization of LRCs in CAES applications.