On April 9, in Haimen, Nantong, at the mouth of the Yangtze River, the "Jianghai," China's largest independently developed shield tunneling machine built jointly by CRCC Heavy Industry, China Railway 14th Bureau Group, and China Railway Siyuan Survey and Design Group, began excavation, marking the official start of the Yangtze River crossing for the Haitai Yangtze River Tunnel project—currently the world's longest underwater highway shield tunnel.

Launch site of the "Jianghai"

It is understood that the Haitai Yangtze River Tunnel project has complex geological conditions. The shield tunneling requires a single-head excavation of 9.3 kilometers over an ultra-long distance, passing through complex geological zones such as silty clay interbedded with silt and composite strata of fine silty sand. The tunnel has a maximum burial depth of about 75 meters and a maximum water pressure of 0.75 MPa, featuring ultra-long distance, ultra-large diameter, ultra-high water pressure, ultra-large burial depth, and complex working conditions, which impose high requirements on the wear resistance and reliability of the cutterhead, cutting tools, and slurry circulation components. When crossing the Yangtze River and the embankments on both banks, the settlement requirements for shield construction are strict, making construction difficult; moreover, the geological exploration coverage in the river is limited, and there are many uncontrollable unknown areas.

In response to the construction risks and difficulties, CRCC Heavy Industry and China Railway 14th Bureau Group formed an R&D team. Drawing on years of equipment manufacturing and construction experience in the fields of underwater and large-diameter shield tunnels, they customized the "river-crossing tool"—the "Jianghai" shield tunneling machine, with a maximum excavation diameter of 16.64 meters, a total length of 145 meters, a weight of about 5,000 tons, and a total installed power of 11,300 kilowatts.

The cutterhead of the "Jianghai" being hoisted at the construction site

The R&D team carried out innovative research on nine major systems, including the cutterhead and cutting tools, main drive, propulsion, and simultaneous grouting. They equipped the machine with a soft-ground cutterhead featuring atmospheric-pressure cutter replacement and cutting tools with large alloy size, high hardness, wide coverage, and strong wear resistance; a retractable main drive; and intelligent equipment systems such as advanced geological prediction, cutterhead wear detection, cutting tool condition monitoring, main drive condition monitoring, and backfill grouting detection systems, maximizing the "measurable, visible, repairable, and replaceable" capabilities of the shield machine's components to ensure safe, efficient, and intelligent excavation. At the same time, the self-developed fourth-generation simultaneous dual-liquid grouting technology was applied, achieving millimeter-level precision control of shield tunnel settlement.

The industry generally refers to shield tunneling machines with a diameter of 14 meters or more as super-large-diameter shield tunneling machines. The "Jianghai" is another super-large-diameter shield tunneling machine independently developed by a Chinese enterprise after the successful application of the 16.07-meter "Jinghua." The launch of the "Jianghai" marks a new leap for China in the development and application of 16-meter-class super-large-diameter shield tunneling machines, and the country has developed the capacity for industrialized development across the entire industrial chain of super-large-diameter shield tunneling machines.

On October 31, 2024, the "Jianghai," China's largest independently developed shield tunneling machine, rolled off the production line at CRCC Heavy Industry

It is reported that the Haitai Yangtze River Tunnel is a key construction project promoted under the "Layout Plan for Yangtze River Trunk Crossing Channels (2020-2035)" and the "Comprehensive Three-Dimensional Transportation Corridor Plan for the Yangtze River Economic Belt of Jiangsu Province." The construction of the project is of great significance for implementing national strategies such as the integrated development of the Yangtze River Delta region and the development of the Yangtze River Economic Belt, optimizing the layout of Yangtze River trunk crossing channels, and promoting the cross-river integrated development of urban agglomerations along the river.