China builds world's largest tunnel boring machine

The 16.64m diameter tunnel boring machine will build a tunnel under the Yangtze River in Jiangsu Province .

China has completed the production of the world's largest tunnel boring machine (TBM), measuring 16.64 meters in diameter . The machine, named Jianghai, weighs 5,000 tons and is 145 meters long. It is also the largest tunnel boring machine designed in China. The machine was manufactured in Hunan Province through a joint venture between China Railway Construction Heavy Industry Corporation (CRCHI) and China Railway 14th Bureau Group, Interesting Engineering reported on November 1.

Tunnel boring machine leaves factory in Truong Sa. (Photo: Global Times).

The TBM has a cutter head diameter equivalent to a 5-6 story building. CRCHI Chairman Zhao Hui said the development marks a major achievement in the industrialization of large-diameter tunnel boring machine technology in China, with a diameter of over 16 meters. The machine's design focuses on operating in fault zones, which can withstand sudden muddy water inflows. Its ring-shaped cutter head enables excavation in extreme conditions, while its dual-mode operation enables simultaneous drilling and blasting, improving speed and efficiency.

The hollow cutting head makes it easier to navigate in complex geological conditions. Researchers at Tsinghua University are expanding the machine's applications to water conservancy, hydropower projects, mining and infrastructure. According to test results, the efficiency of the hollow cutting head can be increased by 30% after cracking in superhard rock.

The new TBM will be used to build a tunnel across the Yangtze River in Jiangsu Province, connecting Nantong and Suzhou. The tunnel is part of a 39-km expressway project scheduled for completion in 2028. Stretching some 11.2 km under the Yangtze River, the tunnel will reach a depth of 75 m.

According to You Shaoqiang, chief engineer of the project at China Railway 14th Bureau Group (CR14G), the tunnel faces many challenges due to underground water, soft soil and mud, making conventional tunneling methods impossible. The advanced TBM will move at a speed of 12-16 meters per day, and the tunneling process will take about 2.5 years. Because the tunnel is located near the mouth of the Yangtze River, the accuracy must be within 1 cm to ensure the safety of dams on the river.

Previously, in 2022, CRCHI and CR14G co-produced a 16.07-meter diameter TBM for a reclamation project in Beijing. According to senior engineer Fan Ruiqiang, it took them more than two years to develop the new, larger TBM. The machine is also smarter, with a database of past tunneling problems, allowing it to provide suggestions to operators when similar challenges arise.