China’s Linghang tunnel boring machine has excavated 89 meters beneath the Yangtze River, setting a new depth record for high-speed rail tunnel construction.
The machine achieved 11.18 kilometers of continuous boring
According to China Media Group, the Linghang shield machine completed 11.18 kilometers of uninterrupted excavation, a global benchmark for sustained tunneling performance. This surpasses previous records set by similar projects in Europe and Japan, where continuous boring rarely exceeded 8 kilometers due to geological interruptions. The feat was enabled by the machine’s autonomous control system, which uses machine learning algorithms to adjust pressure and cutter head speed in real time. Wang Yi, deputy director of equipment at China Railway Tunnel Group, told Science and Technology Daily that the system processes geological data continuously to maintain stability and worker safety. The technology allows the 4,000-ton, 148-meter-long machine to operate with minimal human intervention, even under extreme hydraulic pressure. Last time a comparable milestone was reached, in 2021 with the Gotthard Base Tunnel, progress halted frequently due to unexpected rock fractures, requiring manual recalibration.
High-pressure sealing prevents river infiltration
To maintain structural integrity beneath the Yangtze’s powerful current, engineers deployed a high-pressure sealing system that blocks water ingress into the tunnel bore. This innovation ensures the passage remains dry despite the river’s immense hydrostatic load and complex sediment layers. The seal operates in tandem with the machine’s adaptive pressure control, dynamically countering external forces from the water table above. Without this system, prolonged exposure to water saturation could weaken concrete linings and compromise long-term durability. The sealing mechanism is particularly critical given the Yangtze’s status as one of the world’s most voluminous rivers, with seasonal flow variations exceeding 70,000 cubic meters per second during peak monsoon periods.
For more on this story, see China’s Deepest Undersea High-Speed Rail Tunnel Hits New Milestones.
The tunnel will support 350 km/h high-speed rail
Upon completion, the underwater tunnel will form part of the Shanghai-Chongqing-Chengdu high-speed rail line, enabling trains to operate at 350 km/h continuously. This segment is designed to reduce travel times between major economic hubs in eastern and central China, strengthening regional logistics and economic integration. The dual-track configuration, accommodated by the machine’s 15-meter diameter, allows for bidirectional high-speed traffic without speed restrictions. Chinese officials state the project supports broader national goals of infrastructure-led growth and technological self-reliance in heavy engineering. Similar underwater rail tunnels, such as the Seikan Tunnel in Japan, operate at lower speeds due to stricter curvature and gradient constraints imposed by mountainous terrain.
How deep did the tunnel boring machine move beneath the Yangtze River?
The Linghang machine excavated at a depth of 89 meters below the riverbed, setting a new world record for high-speed rail tunnel construction.
What allows the machine to operate with minimal human intervention?
An onboard artificial intelligence system processes geological data in real time, enabling adaptive control of pressure and cutter head speed without constant manual oversight.