Physical modeling experiment of a novel concrete lining for high-pressure tunnels

The unpredictable development of random cracks in reinforced concrete linings under high internal water pressures poses significant challenges for the operational safety and management of hydraulic tunnels, particularly in water-permeable linings used in pumped storage power stations. To address this issue, this study introduces an innovative structural design: a reinforced concrete water-permeable lining with a prefabricated crack (also referred to as a contraction joint). This design enhances the measurability, controllability, and prevention of crack propagation in high-pressure tunnels, offering a groundbreaking solution to mitigate uncertainty in lining behavior. A custom physical model testing system was developed to simulate the filling and draining processes of high-pressure tunnels, enabling precise measurement of critical parameters such as internal and external water pressures, reinforcement stresses, concrete strains, and crack widths. Physical model tests on linings with prefabricated cracks revealed their operational mechanisms, demonstrating that cracks initiate at predetermined locations during the initial water-filling phase. Subsequently, the lining and reinforcements transition from a tensile to a compressive stress state, effectively preventing the formation of additional random cracks. Throughout operational cycles, the lining remains in compression, with no new crack development. The detailed elucidation of the stress evolution and cracking mechanisms in water-permeable linings, while its engineering significance is underscored by the development of a practical, replicable design and testing methodology. These advancements provide a robust framework for improving the design and management of high-pressure tunnel linings, with broad applicability to pumped storage power stations and similar infrastructure.