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Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Engineers reportedly rescued a stalled 16-meter tunnel-boring machine beneath the Yangtze by driving a second machine from the opposite end of the planned tunnel until the two machines met underground. The reported docking deviation was zero millimeters horizontally and two millimeters vertically—measurements for this operation, not a general industry benchmark.
Where and why the machine stalled
The incident occurred during construction of the 6.4-kilometer Jiangyin–Jingjiang Yangtze River Tunnel in Jiangsu, a highway project intended to connect two industrial zones. The South China Morning Post describes the tunnel as designed to dual six-lane highway standards. Its January 11, 2026 report, citing VnExpress, says the 16-meter shield tunnel-boring machine stalled in February 2023 at about 54 meters (177 feet) underground. That is an approximate reported depth; the accounts do not specify a surveyed depth datum. South China Morning Post
According to the accounts, reversing, repairing, or safely dismantling the machine where it had stopped was not feasible under the conditions. The machine was in water-rich, flowing sand strata under high pressure, making access and recovery difficult. Yao Zhanhu of China First Highway Engineering Co. described the challenge to Science and Technology Daily, as quoted by VnExpress: “The greatest challenge was ensuring the new STM could navigate to the precise location within the high-pressure, water-rich, flowing sand strata,” VnExpress International
How the underground rescue worked
A second machine approached from the other end
Rather than attempt to pull the disabled machine backward or dismantle it in place, the team advanced a second tunnel-boring machine from the opposite end. The two machines were driven toward each other through the ground beneath the river until they could connect. This was a bespoke underground docking operation: the second machine had to reach the stalled one accurately enough to make the connection in difficult ground.
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Navigation and reported docking accuracy
VnExpress reports that the team used a real-time visual navigation system, with cameras and sensors monitoring tunneling progress and environmental data. The machines reportedly connected on July 21, 2025. The South China Morning Post and VnExpress report deviations of zero millimeters horizontally and two millimeters vertically. These are reported figures for this docking operation; the available accounts do not establish them as independently verified measurements or as a broader performance standard.
Stabilization and dismantling
After the machines connected, engineers reportedly stabilized the surrounding area using a method described as “grout first, then freeze.” The machines were later dismantled. VnExpress provides the additional timing, navigation, and stabilization details, attributing some information to other publications; the original project-owner technical report was not available in the reviewed accounts. VnExpress International
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What the reported $50 million figure means
Geoengineer.org’s January 12, 2026 engineering-news article estimates that abandoning the machine would have caused a direct loss of US$50 million. Treat that as an estimate attributed to Geoengineer.org, not as a confirmed purchase price or a figure stated in the accessible South China Morning Post report, which describes the machine as multimillion-dollar equipment without giving that amount. Geoengineer.org
Why use another machine instead of abandoning the first?
Reporting describes several broad possibilities, rather than a formal engineering options analysis. Abandoning the stranded machine could leave costly equipment underground and affect the project; redesigning or cancelling the tunnel would be a much larger project decision. Driving a second machine to meet the first offered a way to reach it without relying on an unsafe or infeasible in-place recovery. The accounts do not provide enough detail to compare schedules, costs, or risks across those alternatives.
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The reported figures make this a striking case of precision tunneling: a second machine reached a stalled 16-meter machine beneath a river, with a reported two-millimeter vertical deviation at docking. They describe one operation on one project. The available sources do not establish industry-wide performance statistics or a general benchmark for underground machine-to-machine docking.
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