Mechanical Behavior of Yielding Steel Lining in Tunnels with High Internal Pressure

The steel lining is a critical structural component in high-pressure tunnels, serving not only as a sealing barrier but also as a load-bearing element that resists a portion of the internal pressure. Its mechanical performance directly influences the operational safety of the tunnel. However, under conditions such as weak surrounding rock, conventional sealing designs based on elastic assumptions often require excessively large lining thicknesses, leading to increased construction costs and an underutilization of the load-bearing capacity of the surrounding rock. To address these limitations, this study introduces a controlled-yielding design of the steel lining. An elastoplastic analytical solution that incorporates the yielding behavior of the steel lining and its interaction with the surrounding rock is developed, enabling a systematic characterization of their mechanical responses during the plastic stage. The results demonstrate that the controlled-yielding design exhibits pronounced advantages under weak surrounding rock conditions, allowing a substantial increase in the ultimate internal pressure capacity of the cavern without increasing the lining thickness. Moreover, under a given internal pressure, the controlled-yielding design can markedly reduce the required thickness of the steel lining. After the steel lining yields, the contact pressure becomes constant as it is governed by the yielding criterion, meaning that the lining’s load-bearing contribution no longer increases even when the surrounding rock becomes weaker. Consequently, the load-sharing ratio of the surrounding rock increases significantly under weak rock conditions, allowing its bearing capacity to be fully mobilized. Overall, the proposed controlled-yielding design of the steel lining provides a new perspective for structural optimization in high-pressure tunnels. It not only enhances the ultimate internal pressure and improves the load-bearing ratio of the surrounding rock, but also reduces the required lining thickness and lowers construction costs, demonstrating substantial engineering applicability.