On January 17, the foundation pit of the key bid section of the Jiangnan connecting line of the Jianning Road Yangtze River Tunnel achieved full bottom sealing across the entire line. This highly anticipated cross-river artery has successfully overcome the most complex underground foundation challenge, and the project has fully shifted into the "fast lane" of main structure construction.

This key bid section is located near Yifengmen. On one side of Jianning Road, traffic flows on the ground, while inside the fenced-off construction site on the other side, there is an entirely different world. Entering the construction area more than 20 meters underground along the stairs from the ground, one steps into a world of steel. Overhead are layer upon layer of thick steel supports, and underfoot are densely arranged steel reinforcement cages. Workers are divided into two groups, continuously pouring concrete into the reinforcement cages beneath their feet amid the roar of machinery.

The project is located in the Yangtze River floodplain area, where geological conditions are extremely complex. The deep foundation pit is adjacent to numerous important buildings, with a large excavation depth and an unusually wide project scope, and a subway will pass beneath it in the future. To ensure smooth construction, the project adopted intelligent detection technology before excavation to address leakage risks in advance, and during excavation used servo and intelligent monitoring systems to control foundation pit deformation.

What is being poured is the last base slab of this bid section, 26 m long, 22–25 m wide, and 1.4 m thick, with 1,000 m³ of concrete. The completion of this pour marks the smooth bottom sealing of the entire foundation pit of this project.

This bid section starts east of Yifengmen and ends near Duolun Road, with a length of about 323 m. Since entering the site in 2022, the project has successively completed pipeline relocation and demolition, as well as retaining structure construction, and began earthwork excavation in November 2024. The foundation pit is up to 31.5 m deep, with a total of 8 levels of supports, and all earthwork was completed over about one year. The main structure is divided into 15 segments for construction, with a total of 60,000 cubic meters of concrete and 15,000 t of steel reinforcement. The first base slab segment was completed in April 2025. After the bottom sealing of the foundation pit this time, the project will fully enter main structure construction.

This structure is a section extending from the cross-river passage toward the surface. The main structure cross-section has four levels and eight cells, with 2 main lines and 2 ramps. The ramps gradually rise from the starting point to the endpoint where they emerge above ground. The structural cross-section is intricate, and with a cover slab coverage rate of 70%, the construction process is extremely difficult. The project adopted optimized support replacement procedures to solve the technical difficulties of space and safety in steel support replacement, and used measures such as custom steel formwork and intelligent curing to improve the structure's impermeability and appearance quality. The project is expected to complete all structural topping-out in September 2026, and then complete the remaining ancillary facilities such as road drainage and pipelines within the year.

The Jianning Road Yangtze River Tunnel and its east extension project directly connect the core area of Jiangbei New Area with the Gulou Riverside area of the Jiangnan main city. Once completed, it will form a free express direct cross-river route. In the future, the drive from Jiangbei Avenue to the Zhongyangmen area in Jiangnan is expected to be shortened to about 15 minutes, effectively diverting pressure from channels such as the Nanjing Yangtze River Bridge and the Yangtze River Tunnel, and truly realizing convenient dialogue between the "twin main cities" of Jiangnan and Jiangbei.