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

A super-large-diameter slurry balance shield machine, developed by China for high-speed railway projects, rolled off the production line in Hangzhou, East China's Zhejiang Province recently, marking a critical phase in the construction of Nanjing's first high-speed railway cross-river tunnel, according to the official WeChat account of China Railway Group on Sunday. 

Measuring 13.72 meters in diameter and 145 meters in length, the shield machine was jointly developed by China Railway Engineering Equipment Group and China Railway Tunnel Group. 

To cope with the project's demanding conditions, the team equipped the machine with advanced features, including a double-layer shell design. Once tunneling is complete, only the backup system and inner shield are extracted, leaving the outer shell as permanent support, enabling the fast and safe disassembly in tight spaces and simplifying later equipment recovery and in-tunnel work.

Nanjing's first high-speed railway cross-river tunnel has a total length of approximately 20.4 kilometers, of which the tunnel section is about 14 kilometers long, designed as a single-tube, double-track high-speed railway tunnel. 

The tunnel runs for an extended distance beneath the Yangtze River bed, with a maximum burial depth of 107 meters and a maximum water pressure of 1.07 megapascals, making it the deepest and highest-pressure railway shield tunnel along the Yangtze River to date.

The cross-river passage will be excavated by two slurry shield machines advancing toward each other from opposite ends, which are scheduled to achieve high-precision docking and on-site disassembly at a depth of 30 meters below the floodplain area on the north bank of the Yangtze River. 

Upon completion, the cross-river passage will alleviate the bottleneck of rail crossings over the Yangtze in Nanjing, and promote the high-quality development of the Yangtze River Economic Belt.

China's Yangtze River Economic Belt, a pivotal economic powerhouse, has seen its regional GDP more than double in the course of the past decade, while steering toward a new path that prioritizes ecological protection and green growth.

Global Times