Automatic health monitoring system for corrosion damage of invert lining of tunnel in salt rock stratum

Strata with high salinity are prone to induce severe corrosion damage at the tunnel invert, seriously threatening structural durability and safety. Conventional monitoring methods cannot meet the requirements for long-term and multiparameter health monitoring under such aggressive conditions. To address this issue, this study proposes an automatic monitoring system for corrosion damage of salt rock tunnel invert by combining weak fiber Bragg grating sensors with multifunctional corrosion sensors. The system enables layered monitoring of both environmental parameters (Cl ⁻ , pH, potential, resistivity) and structural responses (deformation), while an early warning and feedback mechanism is established through wireless transmission. Field application in the China–Laos Railway salt rock tunnel demonstrated that the monitoring system can stably capture chloride intrusion and corresponding deformation at the tunnel bottom. The monitoring results were further cross-validated by ground penetrating radar, and three representative degradation modes under low-, medium-, and high-salinity conditions were identified. These findings reveal the catastrophe mechanism of tunnel invert structures in salt rock strata. The integration of multiparameter sensing, radar verification, and early warning mechanism represents a novel framework for durability assessment and safety management of tunnels in highly corrosive environments.