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China rescued a giant tunnel boring machine (TBM) stuck 54 meters below ground. The operation took place under the Yangtze River in eastern China and illustrates methods for addressing major technical problems during large infrastructure projects.
What the Jiangyin–Jingjiang Tunnel Project Is About
The stuck TBM was part of the ambitious Jiangyin–Jingjiang Tunnel project, which aims to build a 6.4-kilometer road tunnel under the Yangtze. The tunnel sits about 54 meters beneath the riverbed and relies on a modern TBM to cut through the riverbed sediment and form the passage, tell GEO.
That TBM was huge, a 16-meter diameter machine, and expensive, valued at 50 million dollars. During excavation it ran into serious technical trouble and became immobilized. The weight and pressure of the river above made it impossible to use standard methods to fix or dismantle the machine in place.
Facing the Setback
Engineers considered several options. One was to abandon the expensive machine (the fastest route, but a large financial loss). Another was to redesign or cancel the project, which would cause major delays and heavy costs.
They chose a rarely used approach : launch a second, identical TBM from the opposite riverbank and drive it toward the trapped machine. This method, termed “mid-tunnel docking,” required precise guidance and control and involved significant risk.
Tackling the Technical Hurdles
Keeping the second TBM on the exact path was the main challenge. The riverbed is made of waterlogged, easily deformable sediments, so any drift could cause subsidence or water seepage. The job required advanced navigation systems and high precision.
The two TBMs met with a vertical error margin of just 2 mm and negligible horizontal misalignment. Once connected, engineers accessed the stranded machine, secured the tunnel, and continued construction. The rescue saved the project and demonstrated advances in TBM guidance technology and the feasibility of high-precision underground operations.
The response by Chinese engineers demonstrates techniques that can be applied to delicate underwater tunneling. China’s infrastructure program includes over 45,000 kilometers of high-speed rail lines, which provides context for the scale of its engineering efforts. The Jiangyin–Jingjiang Tunnel rescue suggests options for handling complex engineering problems in future projects.
