China's Haitai Tunnel Hits Record 75m Depth

Record-Breaking Tunnel Reaches Deepest Point Beneath the Yangtze

China's Haitai Yangtze River Tunnel has reached its deepest construction point at 75 meters below the riverbed, setting a new national record for super-large diameter shield tunneling. The milestone was achieved as the domestically built 'Jianghai' tunnel boring machine (TBM) completed 5,316 meters of excavation beneath the Yangtze River estuary.

The achievement marks the deepest underwater excavation ever performed by a Chinese-made 16.6-meter-class super-large diameter shield machine, representing a critical breakthrough in the country's tunneling capabilities under extreme conditions.

Engineering Specs Push Boundaries

Dubbed the 'New First Tunnel of the Yangtze,' the Haitai project is currently the world's longest underwater highway shield tunnel. Key specifications include:

• Total length: 39.07 kilometers (24.3 miles)
• River-crossing tunnel section: 11.185 kilometers (6.95 miles)
• Design speed: 100 km/h (62 mph)
• Configuration: 6-lane dual-carriageway expressway
• Maximum depth: 75 meters beneath the riverbed

The tunnel connects Haimen district in Nantong on the north bank to Taicang in Suzhou on the south bank, creating a vital new transportation link across the lower Yangtze River Delta.

Why This Milestone Matters for Global Tunneling Tech

This project demonstrates China's advancing capabilities in 3 critical engineering challenges simultaneously: super-large diameter boring, ultra-high water pressure management, and extreme burial depth construction. These are conditions that push the limits of modern tunneling technology worldwide.

The 16.6-meter-class TBM used in the project is among the largest shield machines operating anywhere globally. Successfully boring at 75 meters depth under a major waterway validates the machine's performance under conditions that few infrastructure projects have attempted.

Implications for Global Infrastructure Development

The Yangtze River Delta is one of the world's most economically productive regions, and improved cross-river connectivity directly impacts logistics and commerce. The Haitai tunnel, once completed, will significantly reduce travel time between the northern and southern banks of the lower Yangtze.

For the global tunneling industry, this project serves as a benchmark. As cities and regions worldwide pursue underwater and underground mega-infrastructure — from the proposed Fehmarnbelt tunnel in Europe to various subsea crossing concepts — China's demonstrated ability to operate super-large TBMs at record depths provides valuable engineering data.

The project continues active construction, with the TBM now past its deepest and most technically challenging section. Completion of the full 39-kilometer route will solidify its status as the world's longest underwater highway shield tunnel.