Mechanical mechanism and composite structure optimization of hard rock hydrogen storage caverns

The lined rock cavern (LRC) offers a promising solution for large-scale hydrogen storage, where mechanical stability and gas tightness are essential for operational safety and efficiency. To address the challenges of evaluating LRC composite structure under complex geological and operational conditions, this study establishes a three-dimensional numerical model and identifies circumferential strain, load-sharing ratio, and structural damage ratio as key evaluation indicators. A Pythagorean fuzzy linguistic cloud (PFLC) model is developed to facilitate quantitative multi-attribute decision-making for assessing and optimizing LRC performance. Results indicate that rock mass strength is the dominant factor, with a correlation coefficient of 77%, and the critical operating pressure remains below the uniaxial compressive strength of the host rock. Based on these findings, a cooperative optimization strategy for the composite structure is proposed: in high-strength rock zones (Class≥II), the lining thickness can be reduced to 0.5 m, and the burial depth can be less than 200 m; C30–C35 ductile concrete is recommended for linings; and reducing the aspect ratio to 5:1 or applying axial reinforcement helps maintain overall stiffness. The proposed multi-objective optimization framework, which integrates geological adaptability and engineering controllability, provides a quantitative basis and theoretical support for the performance evaluation and structural optimization of LRC hydrogen storage caverns.