On the morning of December 7, at the construction site of Shuiximen Street Station on Nanjing Metro Line 9, as the cutterhead slowly rotated, the "Driller No. 1" shield machine began shield tunneling on the right line of the section from Shuiximen Street Station to Qinghe Road Station (hereinafter referred to as the "Shui-Qing section"). This is the first shield tunneling to start on Nanjing Metro Line 9, marking that construction of this line has moved from the station construction stage into the shield tunnel section construction stage.

Phase I of Metro Line 9 runs from Binjiang Park Station in Jianye District in the south to Hongshan Xincheng Station in Xuanwu District in the north, passing through Xuanwu District, Gulou District and Jianye District, with a total length of 19.7 kilometers, all underground. The line has 16 stations in total, including 14 newly built stations and 9 transfer stations, and one Caohoucun depot. At present, hoardings have been erected at 12 stations, of which the main retaining structures at 4 stations have been completed, and structural retaining work is underway at 8 stations.

Li Changchun, deputy director of the Line 9 Engineering Management Office of the Metro Construction Company, said that 10 stations in Phase I of Line 9 are located in the Yangtze River floodplain strata in Hexi. Due to geological conditions, the excavation of station foundation pits and the risks of shield launching and arrival are both very high. At the same time, there are many pipelines within the construction impact area, the space for relocation work is narrow, and the risk of protecting large-diameter water supply and drainage pipelines during construction is high.

The first shield-driven section of Line 9 also involved a "high-difficulty maneuver." Meng Shiqiang, project manager of the China Railway 11th Bureau work area responsible for shield construction in the Shui-Qing section, said that the right line of the first shield-driven section of Line 9 is 1,140.6 meters long. Starting from the shield shaft at the west end of Shuiximen Street Station, it drives westward along Shuiximen Street, then turns south at Yangtze River Avenue into Qinghe Road Station, passing beneath structures such as the Xiawei River box culvert, the Shuiximen Tunnel and the Yangtze River Avenue utility tunnel, while also crossing above and below numerous pipelines along Qinghe Road and Yangtze River Avenue, including communication optical cables, rainwater pipes, sewage pipes and water supply pipes.

Moreover, the shield machine begins "turning" right after launching. The minimum turning radius of the section is 350 m, and the minimum spacing between the left and right line tunnels is only 3.4 m, less than one tunnel diameter. Construction is difficult, risks are high, and tunnel quality control is challenging.

Guo Shiqing, commander of the China Railway Construction general contracting department for Nanjing Metro Line 9, said that the section tunnels are located in the soft soil strata of Hexi, mainly passing through "soft" strata such as mucky silty clay, silty sand, fine silty sand and silty clay interbedded with silty sand. To ensure quality and smooth breakthrough in shield construction, the project department adopted multiple measures at shield launching, including "MJS + vertical freezing + external short sleeve + steel plate-backed segment," to ensure safe shield launching.