沉管隧道壁中热-水-离子传输过程

Thermo-Hydro-Ionic Transport in Walls of Sea Immerged Tube Tunnel

考虑我国东南沿海在建的沉管隧道环境,针对沉管隧道壁所处的特殊环境条件建立了热-水-离子耦合传输模型,研究多离子多场作用下侵蚀性离子在沉管壁混凝土中的迁移过程。利用该传输模型计算了120 a使用期内在不同温度和压力工况下的水分与离子分布。结果表明:隧道壁的水分迁移为内侧干燥过程与外侧海水渗入过程的叠加;温度变化对离子和水分传输的影响比外部水压变化更加显著;120 a隧道外侧溶蚀深度有限,钢筋锈蚀诱发区域深度约为0.65 m,但锈蚀电流低于0.1μA/cm2。

The multi-species transport of ions in sea-water in the concrete wall of immerged tube tunnels was investigated. Concrete immerged tunnels have a long designed life, which are exposed externally to sea-water and internally to traffic air. This particular exposure condition has an important impact on the long-term durability. A thermo-hydro-ionic (THI) model for the ions transport through the tunnel wall that concerns the mass, heat and electrical charge conservations was proposed. The THI model was applied to an ongoing project of immerged tube tunnel on the south-eastern coast of China for a designed life of 120 years for different working cases. The simulated results show that the moisture transport is superimposed by internal drying and external sea-water penetration. The temperature gradient has an more significant effect on the transport processes, compared to the external hydraulic pressure. The external leaching depth is small, the corrosion initiation range attains 0.65 m and the corrosion current is<0.1μA/cm2.