On March 29, 2026, the Linghang tunnel boring machine reached the Yangtze River’s southern bank, completing an uninterrupted 11.18-kilometer lead beneath the riverbed. It began its journey on April 29, 2024, on Chongming Island in Shanghai and emerged in Taicang after 23 months of continuous excavation, a major key stage in large-scale tunnel construction.
The Chinese Ministry of Transport says Linghang completed the longest single-lead excavation by a tunnel boring machine (TBM) of its size, with a 15-meter diameter, without being dismantled or relocated. The planned tunnel length from the initial shaft is 11.325 kilometers; the underwater section measures 11.18 kilometers.
Engineering at Extreme Depths
Weighing around 4,000 tons and stretching 148 meters, Linghang was built to withstand immense pressure nearly 90 meters below the Yangtze. Its 15.4-meter cutting head uses advanced wear-resistant technology to handle abrasive silt and sand. The TBM’s I-TBM intelligent system monitors chamber pressure and machine trajectory while tracking material removal in real time, supporting safe and precise excavation.
As Linghang advanced, it installed prefabricated concrete rings to create a watertight tunnel lining that can withstand pressures of up to 0.9 megapascals. The route crossed the basic river channel and dikes, as well as waterlogged soils and protected fishery zones. The work called for technical innovation and environmental care.
High-Speed Rail Change
Once operational, the Chongtai tunnel will span 14.25 kilometers and carry two high-speed rail tracks in a single gallery. Designed for trains traveling at up to 350 km/h, its large diameter helps limit air-pressure fluctuations, known as the piston effect, which can affect passenger comfort and infrastructure. The design follows approaches used in major European projects, including the Alpine base tunnels, to support smooth high-speed travel.
When the new corridor opens, Chongming will connect directly to China’s high-speed rail network. Suzhou authorities estimate that the trip from Chongming to Shanghai Baoshan station via Taicang could take just 17 minutes. Official project documents put the tunnel’s expected service readiness in the second half of 2029.
The tunnel is part of the North Riverside High-Speed Railway program and a wider regional build-out that also includes the Tong-Su-Jia-Yong High-Speed Railway. Suzhou News reported in October 2026 that broader railway work had reached track-laying and station construction, including at Taicang North Station, and gave 2027 as the expected opening year for the relevant works. That construction phase is separate from the tunnel’s projected service-readiness date.
Record-Breaking, but Not the Largest
Linghang holds the record for the largest-diameter TBM used in a high-speed rail project, but it is not the largest ever built. Guinness World Records lists the Herrenknecht Mixshield S-880 Qin Liangyu, used for a road tunnel in Hong Kong, as the biggest, with a shield diameter of 17.63 meters and a weight of 4,850 tons. Linghang’s achievement stands out for its role in high-speed rail and the distance excavated from a single starting point.
Context and Global Perspective
The tunnel is part of a broader effort to modernize China’s transport infrastructure, alongside ambitious projects such as the Bohai Strait tunnel. Hunan Daily has also identified Linghang as the high-speed railway shield machine operated by Liu Zheyu, born in 2001, framing the project as an example of younger workers taking on demanding infrastructure construction. The scale and complexity of such work echo developments elsewhere, including Russia’s recent advances in submarine technology. The Pacific Fleet’s new Yasen-M class submarine is detailed in this report on Russia's nuclear submarine Perm. Together, these projects reflect the engineering challenges of building beneath water and earth.
The underwater breakthrough ended Linghang’s river-crossing lead, not all tunnelling. Suzhou News reported that the machine later made a second launch to begin excavating the land section, while track and station work advanced across the wider railway project. The remaining work centers on completing the tunnel and delivering the planned high-speed rail connection across eastern China.
