An interior view of the "Linghang" large diameter shield tunneling machine is seen at the construction site of the Chongming-Taicang tunnel, part of the Shanghai-Chongqing-Chengdu High-Speed Railway, under the Yangtze River, on December 16, 2025. Photo: Xinhua News Agency

China's independently developed world's largest-diameter high-speed rail shield machine, the "Linghang" (Navigator) for the Chongtai Yangtze River Tunnel - which connects Shanghai's Chongming district with Taicang, East China's Jiangsu Province - successfully passed under the Yangtze River on Thursday morning. The move signaled the completion of the shield tunnel breakthrough in the water section of the Chongtai Yangtze River Tunnel, while also laying a foundation for China to achieve high-speed trains crossing the river at 350 kilometers an hour without decelerating, the Xinhua News Agency reported on Thursday.

This high-speed rail shield machine, resembling a steel dragon, completed a single-headed excavation of 11.325 kilometers, setting a global record for the longest continuous under-river crossing by a 15-meter-class large-diameter shield machine, news portal thepaper.cn reported on Thursday.

The Chongtai Yangtze River Tunnel is a key section of the Shanghai-Chongqing-Chengdu High-Speed Railway, and is currently one of China's highest-standard and most technically challenging high-speed rail river-crossing tunnel projects, the Xinhua report said. 

The tunnel has a total length of 14.25 kilometers, and features three vertical shafts. The shield tunnel section spanning the Yangtze River waters runs from the No.3 shaft on the north bank to the No.2 shaft on the south bank and has a length of 11.325 kilometers. The maximum burial depth reaches 89 meters below the riverbed, with an ultra-high water pressure of 0.9 Megapascal, and the design speed is 350 kilometers per hour, the Xinhua Daily, a local newspaper in Jiangsu, reported.

The No.2 vertical shaft has been set up on the south bank of the Yangtze River, serving as the reception, maintenance, and secondary launching point for the "Linghang" shield machine. In the next step, based on the No.2 shaft, the project team will carry out in-depth maintenance of the entire "Linghang" shield machine. After that, it will organize the secondary launch of the "Linghang" to complete the final 1.8-kilometer excavation from the No.2 shaft to the No.1 shaft, with the full tunnel breakthrough expected by the end of 2026.

The "Linghang" shield machine has a cutterhead diameter of 15.4 meters, an overall length of 148 meters, and a total weight of approximately 4,000 tons. It is equipped with the I-TBM system - known as the "most powerful brain" for intelligent shield control - along with key components such as a high-water-pressure sealing system, a long-life main bearing, and a wear-resistant cutterhead.

Once the Chongtai Yangtze River Tunnel goes into operation, it will end the history of Chongming Island, China's third-largest island, being without high-speed rail access. It will also take only 17 minutes for a high-speed train journey from Chongming via Taicang to Shanghai Baoshan Station, according to media reports. 

The construction holds great significance for promoting the integrated development of the Yangtze River Delta and improving China's high-speed rail network, according to a post by China Railway.