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

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 tunnel has a total length of about 5,755 meters, featuring 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 the first single-bore, double-deck shield tunnel in China to pass beneath the Yellow River, with the construction route crossing sensitive areas including the Yellow River embankment and the river itself.

The project overcame 28 major technical challenges, including excavation stability control, 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 improvements in technological capabilities and accelerating global expansion.

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 tunnel boring machine industry is moving from large-scale application toward higher levels of intelligence, efficiency and global competitiveness.