China Deploys Frontier Tech in World’s Longest Undersea Rail Tunnel
China is pushing the boundaries of underwater engineering with the application of multiple frontier technologies in the construction of the Jintang Undersea Tunnel, part of the Yongzhou Railway connecting Ningbo and Zhoushan in Zhejiang Province. The project, which Xinhua reports, incorporates intelligent tunneling systems, AI-driven decision-making models, and domestically developed deep-sea pressurized equipment to drive the world’s longest undersea high-speed railway tunnel toward unmanned and intelligent construction.
A Record-Breaking Engineering Feat
The Jintang Undersea Tunnel is the flagship control project of the 76.4-kilometer Yongzhou Railway, a high-speed line designed for 250 km/h that is part of China’s national Medium and Long-term Railway Network Plan. The tunnel spans 16.18 kilometers—with a shield tunneling section of 11.21 kilometers—running from Ningbo Beilun in the west to Zhoushan Jintang in the east beneath the Jintang Waterway, as China Daily documented when the project began.
Two super-large diameter shield machines, the “Yongzhou” and the “Dinghai,” are tunneling simultaneously from opposite ends of the seabed, with plans to meet at a high-precision connection point approximately 78 meters below sea level—equivalent to 26 stories deep. The tunnel faces extreme conditions, including maximum water-soil pressure of 8.5 bar and geological challenges that include 24 alternating soft/hard strata transitions, with hard rock and uneven soft-hard strata accounting for nearly 70 percent of the route, according to SASAC.
Intelligent Systems Take the Lead
At the First Large Shield Tunneling Summit held in Ningbo on August 29, Chinese Academy of Engineering academician He Chuan revealed that the “Large Shield Intelligent Driving System”—which aggregates tunneling data from one-third of all large shield tunnels nationwide—is now being trained and tested at the Jintang Undersea Tunnel. The system integrates three intelligent modules for on-site sensing, automatic tunneling, and condition assessment, allowing remote monitoring and even fully automatic shield tunneling when conditions are stable.
Complementing this is the “Shenyuan Large Model,” China’s first ultra-large-scale mixed expert model for large shield tunneling. Now in trial use, the model integrates massive construction data and more than 800,000 professional documents, using AI-driven scheduling to support intelligent decision-making in risk prevention, safety control, and tunneling supervision.
The “Deep Sea Space Station” Breakthrough
Perhaps the most striking innovation is the “Deep Sea Space Station,” China’s first domestically developed saturated pressurized work equipment for shield tunneling. Developed jointly by China Railway 14th Bureau and the Ministry of Transport’s Shanghai Salvage Bureau over three years, the system enables workers to live and work in high-pressure seabed environments for extended periods, as CNR/Science and Technology Daily detailed.
The equipment includes living, shuttle, and control cabins with fully domestically developed core systems for pressure control, gas management, life support, and emergency response. On August 17, it completed 104 cutter inspections and replacements at 80 meters depth under 7.8 bar water pressure, setting a national record for maximum pressure in shield pressurized entry operations.
“Workers enter the isolated ‘Deep Sea Space Station’ and live in the living cabin, equivalent to ‘settling down’ on the seabed,” said Wu Yuli, a shield tunneling expert at China Railway 14th Bureau, as Xinhua reported during the equipment’s first application in February. In that initial deployment, nine workers stayed at 75 meters depth for 22 days, replacing 46 cutters.
The cutter replacement challenge is immense. “Cutters are the ‘teeth’ of the shield machine,” explained Han Fengqi, chief engineer of the project, in an interview with Guangming Online. “In this seabed ‘tooth-grinding’ stratum, we must constantly ‘replace teeth’ for it. So far, we have cumulatively replaced more than 3,000 cutters, averaging about one cutter per meter of tunneling.”
Strategic Significance
Beyond the engineering achievement, the project carries significant strategic weight. The Yongzhou Railway, expected to be operational by 2028, will end Zhoushan’s history of having no railway connection—making it the last prefecture-level city in the Yangtze River Delta to join the national rail network. It will also link the two major ports of Ningbo and Zhoushan, opening logistics channels from the Yangtze River Delta coastal area to inland regions, as Zhejiang Online noted.
As of mid-March, total shield tunneling had exceeded 9,000 meters, completing 80 percent of the task. The two shield machines are expected to meet at the seabed connection point by late 2026.
The Future of Intelligent Tunneling
Qian Qihu, winner of China’s Highest Science and Technology Award and a Chinese Academy of Engineering academician, outlined the road ahead at the summit. “Looking to the future, intelligence will become an important direction for the shield tunneling engineering field,” he said. “The next step requires further improving the technical level of intelligent cutter-changing robots, promoting the automation and intelligence of shield tunnel segment assembly, enhancing automatic sensing and control capabilities for fault risks, and further expanding the application of intelligent technology in complex tunnel engineering construction.”
With the “Deep Sea Space Station” filling a domestic technology gap and AI systems now being deployed on-site, the Jintang Undersea Tunnel is not just building a railway—it is establishing a template for how China will approach deep-buried tunnels, cross-sea passages, and subsurface infrastructure development for decades to come. As the People’s Daily reported, these frontier technologies are driving the project toward a future of unmanned, intelligent construction that could reshape the global tunneling industry.