On the morning of December 7, as the cutterhead of the 'Xinyue' shield machine slowly rotated, the shield machine for the Jiajiang River crossing section of the Nanjing Jiangxinzhou Sewage Collection System Phase II Construction Project, undertaken by China Railway 14th Bureau Group, was successfully launched, marking the project's official transition into the shield tunneling stage.

The Nanjing Jiangxinzhou Sewage Collection System Phase II Construction Project starts on the west side of Citizens' Square in Jiangxinzhou, Jianye District, Nanjing. It crosses the Jiajiang River and enters Binjiang Park, ending at the Jiangnan working shaft, where it connects with the existing sewage channel. The project is currently China's largest-diameter sewage river-crossing shield tunnel. The project route has a total length of 755.6 meters, including a shield tunnel length of 693 meters, with a segment outer diameter of 8.8 meters. The 'Xinyue' shield machine, with an excavation diameter of 9.15 meters, is used for tunneling.

Along the route, the tunnel mainly crosses the embankments on both banks of the Jiajiang River, the Jiajiang River itself, existing bridge abutments, and various pipelines. There are many risk factors with significant impact. Limited by the structural dimensions of the launch shaft, the shield machine adopts a split launch method, resulting in high construction difficulty and risk.

To improve tunnel construction quality and reduce later operational risks, the project adopts a variety of new domestic technologies. The segments innovatively use new socket-type connectors, which are convenient and quick to install and significantly improve the structural stress, waterproof performance, and appearance quality of the formed tunnel; their advantages and application prospects are of great significance. A new two-component grouting process is used for simultaneous segment grouting, leveraging the fast setting rate and high consolidation strength of two-component grout to reduce segment uplift and misalignment and improve tunnel formation quality. At the same time, the segments adopt double-seal waterproofing, providing dual protection and more effectively improving segment waterproofing quality.

To strengthen the research and application of new technologies, the project department established a Party member innovation studio, gathering the project's scientific research strength. It conducts analysis and research on topics such as 'new socket-type segment prefabrication technology,' 'simultaneous two-component grouting,' and 'intelligent construction advancement,' bringing construction risks under control before shield launch and safeguarding the smooth progress of the project.

It is reported that after the project is completed, it can directly transport about 400,000 cubic meters of sewage per day from the main urban area of Nanjing to the Jiangxinzhou Sewage Treatment Plant. It will improve the drainage economy of the river-crossing channel and the safety and reliability of the existing main channel's operation, benefiting 1.74 million residents in the Inner Qinhuai River basin, the Outer Qinhuai River Shuangqiaomen to Sancha River interception system, and the Hexi New Town area.