Recently, at the Nantong section of Jiangsu Province near the Yangtze River estuary, the Haitai Yangtze River Tunnel—designed by China Railway Siyuan Survey and Design Group Co., Ltd. and constructed by China Railway 14th Bureau Group Co., Ltd.—was excavated to its lowest point, 75 m below the riverbed. This sets the deepest underwater excavation record for a domestically produced 16.6-meter-class super-large diameter shield machine, as well as the deepest excavation record for the largest-diameter Yangtze River tunnel in China. It marks a crucial breakthrough in China’s underwater shield construction technology under conditions of super-large diameters, ultra-high water pressure, and super-deep burial.

The Haitai Yangtze River Tunnel project has a total length of 39.07 km, connecting Haimen in Nantong to the north and Taicang in Suzhou to the south, with the cross-river tunnel section measuring 11.185 km long. This tunnel is currently the world’s longest underwater highway shield tunnel, as well as China’s largest-diameter Yangtze River tunnel, and is hailed as the “The First New Tunnel of the Yangtze River.”

The working face at the lowest point of the tunnel beneath the riverbed withstands a composite water and soil pressure of up to 7.5 bar. The hydrogeological conditions beneath the main channel of the Yangtze River are extremely complex. The construction process faces multiple challenges, including the enrichment of confined water in the strata, high permeability coefficients, and the rapid wear and tear of cutting tools in the highly abrasive strata at the river bottom. These factors impose high requirements on the correction of the excavation posture, as well as the compactness and precision control of synchronous grouting.

The project team established a three-level guarantee system. The shield machine is equipped with advanced core devices, such as atmospheric-pressure blade changing technology and a telescopic main drive. Relying on an intelligent monitoring system to dynamically optimize parameters, the team has achieved refined and intelligent excavation. Currently, the shield machine has successfully completed its 5,316-meter excavation task. After passing the lowest point, it has transitioned from “diving deep downward” to “heading upward,” entering a new stage of excavation. As a key project of the Planning of Cross-River Channels on the Mainstream of the Yangtze River (2020–2035), the Haitai Yangtze River Tunnel, once completed, will significantly shorten the travel time between Nantong, southern Jiangsu, and Shanghai, promoting efficient interconnectivity within the “one-hour economic circle” of the Yangtze River Delta’s core area.