Influence of host-rock plasticity on deformation, stability, and liner detachment in pressurized lined rock caverns

Lined rock cavern (LRC) offer a promising solution for underground hydrogen storage, which requires high pressure (>200 bar) to ensure economic viability due to hydrogen’s low volumetric density. In LRCs, the liner acts solely as a gas seal, while the rock mass bears the structural load. However, at economically feasible shallow depths (< few hundred meters), the high storage pressure significantly exceeds the low in-situ stress (on the order of 10 bars), creating a critical containment challenge.

Achieving safe containment under such a pressure difference requires accurate assessment of the mechanical strength of the rock mass. A criterion often used is to limit the load below the level when plastic deformation occurs. In many cases, however, this criterion still yields safe gas pressure which are below the desired level. Increasing gas pressure above this level means that some degree of plastic deformation will occur in the rock mass. This can take the forms of continuous deformation, jointing, or cracking.

Our knowledge from rock deformation experiments and LRC pilot sites indicates that there exists a safe level of inelastic deformation before storage integrity is compromised. However, the critical challenge lies in identifying how such inelastic deformation initiates, evolves, and redistributes under high internal pressure, as well as its implications for long-term cavern stability. Consequently, the mechanical response of the surrounding rock under high internal pressure remains a key uncertainty in stability assessment. Simplified elastic rheological models, which are commonly used in engineering design, may mask irreversible deformation processes in the near-field region of the cavern. In this study, a visco-elastic–viscoplastic (VEVP) model is employed to systematically investigate the mechanical behavior of the surrounding rock under cyclic gas pressurization, with particular focus on the role of rock plasticity. Model predictions are quantitatively compared with those obtained from a purely elastic formulation by varying the rock cohesion parameter. Under baseline conditions, the maximum radial displacement predicted by the VEVP model is 53% higher than that predicted by the elastic model, while the maximum circumferential strain increases by 186%. With the development of plasticity, the spatial distributions of strain and displacement evolve significantly. During the elastic stage, maximum circumferential strain is aligned with the principal stress directions, whereas maximum radial displacement occurs along directions oriented at 45° to the axes. As plastic deformation develops, the dominant deformation zone migrates toward the axial directions where plastic flow becomes most pronounced. Furthermore, plasticity-driven stress redistribution leads to stress relaxation and homogenization of deviatoric stress, accompanied by directional migration of pressure-dominated zones. Finally, the VEVP model elucidates a mechanical mechanism for potential lining–rock debonding caused by modulus mismatch. Upon depressurization, the steel lining undergoes nearly complete elastic rebound, while the surrounding rock retains irreversible plastic deformation, leading to asynchronous recovery and possible interface opening. These findings highlight the necessity of accounting for rock plasticity when assessing the mechanical stability and design of lined rock caverns for underground hydrogen storage.