A double-deck underwater tunnel with the world’s largest diameter has been put into operation in Jinan, East China. Crossing the Yellow River by car now takes five minutes instead of the previous 30-40.
The tunnel is 5,755 meters long, with a designed speed of 60 kilometers per hour. Traffic runs on two levels within a single bore. It is China’s first tunnel of this type passing beneath the Yellow River, with the route crossing difficult sections including the embankment and the riverbed itself.
Engineers had to solve 28 major technical challenges: ensuring excavation stability, controlling settlement beneath the embankment, preventing uplift of large-section tunnel segments, and arranging green treatment of massive volumes of slurry (waste).
Shield tunneling technology relies on a tunneling shield — a special metal structure that holds back the surrounding soil. The shield section, stretching about 3,290 meters, was built using a tunnel boring machine with an excavation diameter of 17.5 meters. The maximum excavation rate reached 18 meters per day, with a monthly advance of 426 meters — a world record for 17-meter-class machines.
The Jinan tunnel is not the first application of this technology. On July 30, Linghang, the world’s largest-diameter high-speed-rail shield tunneling machine, successfully completed the underwater section of the Chongming-Taicang Yangtze River Tunnel. This lays the groundwork for China’s first high-speed rail line to cross beneath the river without slowing down, at 350 kilometers per hour.
According to Chinese experts, shield tunneling machines are a core piece of equipment for underground engineering. The industry is moving from large-scale application toward higher levels of efficiency and global competitiveness.
