How China rescued highway project under Yangtze River after a US$50M tunnel-boring machine stalled

The incident occurred in February 2023 during construction of the 6.4-kilometer Jiangyin–Jingjiang Yangtze River Tunnel. Midway through excavation, at a depth of 54 meters, a 16-meter-diameter shield tunnel-boring machine suddenly ground to a halt, according to the South China Morning Post.

With no safe way to repair or reverse the machine, and under extreme water pressure, the $50 million equipment was effectively trapped underground, bringing the entire project to a standstill.

The failure occurred directly beneath the Yangtze River’s main shipping channel, where water pressure at that depth approached 0.76 megapascals, exerting a force of about 77 tonnes per square meter against the machine’s shield.

Engineers warned that the situation risked turning the large-scale infrastructure project into a disaster. Project leaders faced stark options: abandon the machine and absorb the loss, redesign the tunnel entirely, or cancel the project, each scenario implying years of delays and serious disruption.

A tunnel boring machine in China. Photo from X

After consultations with the Chinese Academy of Engineering, the project team chose a third, unprecedented solution: deploying a second, identical tunnel-boring machine from the opposite end to dock with the stalled machine beneath the river, Interesting Engineering reported.

"The greatest challenge was ensuring the new STM could navigate to the precise location within the high-pressure, water-rich, flowing sand strata," Yao Zhanhu of China First Highway Engineering Co told the Science and Technology Daily on Jan. 7.

Six months after the malfunction, the second machine began advancing slowly from the opposite side of the tunnel. Engineers had to predict ground movement beneath the river while controlling the machine’s direction over several kilometers with millimeter-level accuracy. To meet these requirements, the team developed a real-time visual navigation system, using cameras and sensors to collect tunneling and environmental data for continuous monitoring.

On July 21, 2025, the two machines successfully connected beneath the Yangtze River, aligning almost perfectly. The horizontal deviation at the junction was 0 millimeters, while the vertical deviation measured just 2 millimeters.

Following the successful docking, engineers stabilized the connection zone using a method described as "grout first, then freeze." The team used freezing pipes as drill rods, combining drilling, grouting, and freezing to secure the construction joint and prevent collapse or flooding.

The final step involved dismantling the two massive tunnel-boring machines. Each 16-meter machine was manually cut into roughly 2,000 components and at the same time, concrete was injected into the tunnel’s outer ring to ensure long-term structural stability.

On March 26, the main structural linings at both ends of the tunnel were fully connected, with construction teams from each direction meeting underground. By late November, the underwater docking section of the Jiangyin–Jingjiang Yangtze River Tunnel was officially completed.

The tunnel is expected to fully open by the middle of this year. Built to six-lane expressway standards, it will become China’s largest-diameter tunnel and the one designed to withstand the highest water pressure once operational.