On October 31, a ground breaking shield machine with an excavation diameter of 16.64 meters—the largest Chinese made —rolled off the production line in Changsha, Hunan. This machine will be instrumental in constructing the world's longest underwater highway shield tunnel, the Haitai Yangtze River Tunnel. Following the successful production of the first 16-meter-class super-large shield machine, "Jinghua," CRCHI has once again surpassed itself, setting a new record with Jianghai, marking a significant milestone in the development of large-diameter shield machines in China.
Named "Jianghai" to symbolize its journey across the Yangtze River and its proximity to the sea, the shield machine is 145 meters long and weighs approximately 5,000 tons. The cutter head is painted with blue waves, representing the power and resilience required to tackle the challenging underwater conditions.
The Haitai Yangtze River Tunnel is located at the Yangtze River estuary in Jiangsu Province, connecting Haimen District in Nantong to Taicang City in Suzhou. The project spans a total of 39.07 kilometres, including an 11.185-kilometer cross-river tunnel. Designed as a two-way, six-lane highway, it has a speed limit of 100 kilometres per hour. The tunnel section extends 9,315 meters and will require excavation at a diameter of 16.64 meters. It must pass through complex geological layers, including silty clay interbedded with silt and fine sand, with a maximum burial depth of 75 meters and water pressure reaching up to 7.5 bars. This demanding environment poses challenges such as long distances, high water pressure, and difficult geological conditions.
Jianghai is engineered to tunnel continuously over long distances under the Yangtze River. Particularly challenging will be crossing the river and the surrounding dikes, where ground settlement must be kept within 1 centimetre. With limited geological data for some underwater sections, the project faces numerous unknowns and high construction risks. The massive diameter of 16.64 meters requires significant torque for excavation, and the main drive bearing must withstand heavy loads. Components such as the main drive seal and tail seal must be able to withstand water pressure as high as 7.5 bars. Maintaining continuous tunnelling performance for 9,315 meters in such an environment is a primary challenge for the R&D team.
To address these challenges, the R&D team has designed several specialized features for Jianghai. The machine is equipped with a cutter head suitable for soft soil, fitted with large, durable alloy cutters to ensure effective excavation. The main drive has a telescopic function to sense the cutter head's load, preventing overload on the main bearing and facilitating cutter changes when needed. Additionally, a monitoring system tracks the main drive's status to prevent breakdowns. The machine's structural thickness, oil cylinder specifications, slurry circulation system, and grouting system have all been optimized to enhance performance. A smart assembly system for segment connections is also included to meet construction requirements.
Scheduled for completion in 2028, the Haitai Yangtze River Tunnel is a critical infrastructure project. Once operational, it will help ease traffic on the Suzhou-Nantong Yangtze River Bridge and play an essential role in optimizing transportation routes across the Yangtze River. For further information please visit https://en.crchi.com/. 45/24.
