China's mega tunneling machine completes Yangtze River underwater tunnel breakthrough

SHANGHAI -- The world's largest-diameter shield tunneling machine, tailored for high-speed railway projects and developed domestically in China, successfully holed through an underwater tunnel traversing the Yangtze River on Thursday.

The breakthrough will allow a high-speed train to run beneath the Yangtze River at a full speed of 350 km per hour without slowing down for the first time, marking a landmark progress in China's river-crossing railway tunneling technology.

With a total length of 14.25 kilometers, the tunnel connecting Shanghai's Chongming district and Taicang city in neighboring Jiangsu province is built according to the highest construction standards among China's high-speed rail river-crossing projects, while ranking among the most technically challenging mega infrastructure works of its kind.

Li Bin, chief engineer of the tunnel project with China Railway Tunnel Group Co., Ltd., noted that the 148-meter-long shield machine weighs around 4,000 tonnes and features a 15.4-meter ultra-large cutter head, making it the world's largest-diameter tunneling equipment for high-speed railway construction.

The unmanned tunneling gear achieved a single continuous underwater drive of 11.325 kilometers under the Yangtze, setting a new domestic record for 15-meter-level shield tunneling.

The full completion of the entire tunnel is scheduled by the end of 2026. Once put into operation, the project will end the island district of Chongming's lack of high-speed rail access, and cut travel time from Chongming via Taicang to Shanghai's Baoshan Railway Station to just 17 minutes, significantly improving regional transportation connectivity.