On January 4, with the completion of the final pour of concrete, all base slabs of the main structure of the Jiangxinzhou intermediate ventilation shaft on Phase II of Nanjing Metro Line 4 were completed, meaning the main structure has been successfully built, providing the necessary conditions for the shield tunneling machine to cross the Yangtze River next. This ventilation shaft is about 44 meters deep and is a controlling project of Phase II of Line 4, as well as the deepest foundation pit in soft soil strata among Nanjing Metro projects.

Phase II of Nanjing Metro Line 4 starts at Zhenzhuquan Station in Pukou District and, after crossing the Yangtze River, connects to Longjiang Station on Phase I of Line 4. Once completed, it will greatly enhance Nanjing Metro's service capacity for passenger flows between the two main urban areas south and north of the Yangtze River. Phase II of Line 4 is about 10 kilometers long, entirely underground, with 6 underground stations, including 2 transfer stations. Among them, the Jiangxinzhou intermediate ventilation shaft reserves conditions for a future station and is a key and difficult controlling project for the entire section's construction.

According to on-site project engineers, ordinary foundation pits on the Nanjing Metro are only 20 to 25 meters deep, equivalent to an 8-story building, but the foundation pit of the Jiangxinzhou intermediate ventilation shaft is about 44 meters deep, equivalent to a 15-story building, making it arguably the deepest soft-soil foundation pit in the history of the Nanjing Metro.

The ventilation shaft is adjacent to the Yangtze River and the Jiajiang River, surrounded by water on three sides, and located at the northernmost tip of Jiangxinzhou, less than 200 meters from the river embankments on its east and west sides. The ultra-large depth and special location have brought a series of challenges to construction. Since the construction of the first diaphragm wall in October 2021, Nanjing Metro, together with all participating units, has carefully studied construction plans, planned ahead for essential safety and quality control points, and efficiently organized the coordinated construction of all teams and processes. After 862 days and nights of continuous effort, the metro builders ensured continuous earthwork excavation and completed the main structure of the upper three levels by open-cut top-down construction and the lower two levels by covered cut-and-cover reverse construction, successfully achieving the milestone target.

The "main frame" of this ventilation shaft consists of 66 reinforced concrete diaphragm walls that are 64.5 meters deep, 1.5 meters thick, and have cages weighing 180 tons. Outside the diaphragm walls, water-stop plain concrete walls of the same depth and 0.8 meters thick were also built, using a double barrier to isolate river water and sand. The permanent concrete-filled steel tubular structural columns inside the ventilation shaft play a crucial role in structural stability, and their verticality should reach one-thousandth. With the help of innovative equipment such as a universal verticality adjustment platform and inclinometers, and following strict quality control procedures, construction personnel achieved high-precision installation of ultra-deep, large-diameter concrete-filled steel tubular columns, enabling the actual verticality of the permanent structural columns to reach two ten-thousandths, far exceeding the standard.