China's largest tunnel boring machine — with a diameter of 16.64 meters — rolled off the production line in Changsha, Hunan province on Thursday.

The machine, weighing around 5,000 metric tons and 145 meters long, is the largest TBM designed in the country and has been named Jianghai — the Chinese equivalent of river and ocean.

The machine is jointly developed by China Railway Construction Heavy Industry Corp Ltd and China Railway 14th Bureau Group Co Ltd (CR14G), both units of China Railway Construction Corp, a centrally administered State-owned enterprise.

The TBM will be used for building a tunnel across the Yangtze River linking Nantong and Suzhou in Jiangsu province.

The tunnel is a section of a highway spanning 39 kilometers, which is expected to finish construction in 2028. The tunnel under the river, with the deepest areas reaching 75 meters underground, is some 11.2 km long.

Meanwhile, the tunnel is situated in areas with underground water sources, soft earth and silt, which make it impossible to use traditional manual tunneling methods, said You Shaoqiang, chief engineer of the project at CR14G.

The machine can advance 12 to 16 meters per day, and it will take about two-and-a-half years for the tunneling to be completed, he said.

As the tunnel is situated at the estuary of the Yangtze River, the precision of the tunneling area needs to be kept within 1 centimeter in order to protect the safety of dams across the river, the engineer said.

In 2022, a TBM with a diameter of 16.07 meters was manufactured by the two companies, which has been used for a renovation project in Beijing.

Fan Ruiqiang, senior engineer at CRCC's heavy industry arm, said it took the research team more than two years to make the new and largest TBM.

The new TBM is also more intelligent and comes equipped with a database that contains previous problems in tunneling. This means the machine can offer suggestions to drivers when similar problems occur, he said.

Wang Jun, deputy head of the Jiangsu transport project construction bureau, said the new machine marks the first step in the construction of the highway, which is a major transport infrastructure for the province.

The new machine is also a major breakthrough in China's manufacturing industry and showcases the hard work of engineers and previous achievements in the sector, Wang said.

The successful manufacturing of the larger TBM with new technology and materials shows China's industrial upgrading. The constant breakthroughs in TBM technology have improved the country's influence and competitiveness in the sector, he added.

zoushuo@chinadaily.com.cn