Plastic Damage Analysis and Structural Optimisation of Reinforced-Steel Fibre Concrete Lining for Underground Gas Storage Caverns

Underground Compressed Air Energy Storage (CAES) is a promising large-scale energy storage technology, yet its long-term operational safety is constrained by progressive tensile damage accumulation in lining structures under cyclic thermo-mechanical loading. Conventional steel-lined caverns are costly, while ordinary reinforced concrete linings require excessive reinforcement due to their limited tensile capacity, compromising the economic viability of CAES. This study proposes a Reinforced-Steel Fibre Concrete (R-SFC) lining as the structural load-bearing layer of CAES caverns, in which the steel fibres provide tensile and crack-propagation resistance and the rebars contribute supplementary tensile capacity. A 2D coupled thermo-mechanical damage-plasticity finite element model was developed in COMSOL Multiphysics and verified using published in situ monitoring data from operating CAES caverns. Parametric analyses of the steel fibre volume fraction, lining thickness, rebar diameter, and cavern diameter were then performed. The results show that the R-SFC lining significantly improves crack propagation resistance, reducing the maximum tensile damage by 41.3% relative to conventional reinforced concrete while lowering steel consumption. Within the lining–rock system, the concrete lining and the surrounding rock jointly resist the radial compressive load, while the steel fibres and rebars bear the hoop tensile stress. A thickness-to-diameter ratio of 1/8 to 1/5 is identified as the recommended geometric design range to balance lining damage against surrounding rock loading. Finally, an MOPSO algorithm coupled with a PSO-BP surrogate model is employed to balance lining tensile damage against cavern dimensions, yielding optimised parameter combinations particularly suitable for cavern diameters around 4 m. The study findings may provide a new lining solution and design reference for cost-effective and high-reliability underground gas storage.