On September 8, as the cutterhead of the "New Journey" shield machine began to rotate, shield tunneling commenced on the river-crossing tunnel section of Phase II of Nanjing Metro Line 4.

Phase II of Nanjing Metro Line 4, an important transportation artery running north-south across the Yangtze River, has carefully planned 6 stations, including 2 key interchange stations, aimed at further optimizing the public travel experience and improving public transport efficiency. Of particular note is the river-crossing tunnel section constructed by China Railway 14th Bureau Group, which serves as the controlling project of the entire line. Starting from the intermediate ventilation shaft on Jiangxinzhou, it has overcome challenges by passing beneath the Jiangxinzhou Yangtze River levee and forging through the Yangtze River main navigation channel, before finally being received successfully on the north bank. With a total length of an astonishing 3,062 meters, it demonstrates the extraordinary strength of the engineering construction.

It is particularly worth mentioning that the tunnel must extend 2,200 meters through the mid-river section of the Yangtze River, tunneling to an extreme depth of 68.58 meters below the Yangtze River water surface. This depth sets a new record for river-crossing metro tunnel construction in the Yangtze River Delta region and undoubtedly represents an extreme challenge to engineering technology. The strata the tunnel passes through are mostly water-rich soft soil, and the complex and variable geological conditions further add to the difficulty and uncertainty of construction.

In the face of numerous difficulties, the project team customized the "New Journey" shield machine. With an excavation diameter of 11.64 meters, a total weight of more than 2,100 tons, and a total body length of 120 meters, this shield machine is a leader in the field of domestic metro tunnel construction. Particularly innovative is its onboard simultaneous dual-liquid grouting system, the first application of this system in domestic river-crossing metro tunnel construction. It effectively solves the problem of segment flotation, greatly improves construction safety and efficiency, and provides a solid guarantee for the quality of the completed tunnel.

Phase II of Nanjing Metro Line 4, as the fourth river-crossing metro line after Nanjing Metro Line 3, Line 10, and Phase I of the Ninghe Intercity Line, is not only a further improvement of Nanjing's urban rail transit network, but also an important measure to promote integrated cross-river urban development, alleviate cross-river traffic congestion, and foster sustainable regional socioeconomic development.