The world's largest-diameter underwater shield tunnel has been completed and officially put into operation in Jinan city, East China's Shandong Province on August 25, 2026. Photo: Xinhua News Agency

The world's largest-diameter underwater shield tunnel has been completed and put into operation in Jinan, East China's Shandong Province, the Xinhua News Agency reported on Tuesday.

The 5,755-meter-long tunnel features a single-bore, double-deck design with a designed speed of 60 kilometers per hour. The shield section stretches about 3,290 meters and was constructed using a tunnel boring machine (TBM) with an excavation diameter of 17.5 meters. 

The tunnel is China's first single-bore, double-deck shield tunnel passing beneath the Yellow River, with the construction route crossing sensitive areas including the Yellow River embankment and the river itself.

After the tunnel opens to traffic, the travel time for vehicles crossing the Yellow River will be cut from about 30-40 minutes to about five minutes.

Engineers overcame 28 major technical challenges, including control of excavation stability, settlement control when passing beneath the Yellow River embankment, uplift control of large-section tunnel segments, and green, efficient treatment of massive amounts of slurry. It achieved a maximum daily excavation rate of 18 meters and a monthly advance rate of 426 meters, setting a world record for 17-meter-class shield tunneling.

In recent years, China's shield tunneling industry has seen continued market expansion, significant technological improvements and accelerating global expansion.

Rapid advances in China's shield tunneling technology have enabled a growing number of technically challenging projects. On July 30, Linghang, world's largest-diameter high-speed-rail shield tunneling machine, successfully completed the underwater section of the Chongming-Taicang Yangtze River Tunnel, laying the groundwork for China's first high-speed rail line to cross beneath the Yangtze River at 350 kilometers per hour without slowing down, according to another Xinhua report.

As a core piece of equipment for underground engineering, shield machines have entered a growth phase driven by both domestic demand and exports, Chinese experts said. Technological advances are enabling rapid breakthroughs in engineering projects, while China's TBM industry is moving from large-scale application toward higher levels of intelligence, efficiency and global competitiveness.

Global Times