On October 22, construction workers from China Railway Eleventh Bureau were busy assembling tunnel segments at the Jintang Undersea Tunnel of the Ningbo-Zhoushan Railway. The 10:00 AM milestone marked a significant breakthrough as the “Dinghai” shield machine successfully crossed the seawall and transitioned from the land section to the underwater segment, officially kicking off the construction of the world’s longest undersea high-speed railway tunnel.
Located beneath the Jintang Channel between Ningbo and Zhoushan, the Jintang Undersea Tunnel is a key project of the Ningbo-Zhoushan Railway. It stretches 16.18 kilometers, making it the longest underwater high-speed railway tunnel in the world, with 11.21 kilometers of its length constructed using the shield tunneling method.
Since its simultaneous launch from both sides on May 16, the “Dinghai” and “Yongzhou” shield machines have been digging towards each other, with the “Dinghai” machine aimed at advancing 6,270 meters from east to west, and the “Yongzhou” machine drilling 4,940 meters from west to east. The two machines are set to meet at the seabed after navigating high water pressure and various complex geological conditions.
Currently, the “Dinghai” machine has achieved the “zero-subsidence” goal as it advances at an impressive pace of 16 meters per day, nearing the 1,000-meter mark. Meanwhile, the “Yongzhou” machine has completed 902 meters of tunneling in the land section and is expected to enter the underwater phase by May of next year.
During the transition to the underwater construction phase, the “Dinghai” shield machine will need to navigate potential risks such as seawall protection, the entanglement of drainage sheets with the cutter head, and the challenges posed by crossing navigable waterways and anchorages. Addressing complex geological challenges like cutter head clogging, tool wear, and maintaining airtight seals under high water pressure will be critical, along with ensuring precise tunneling across long distances. The Shanghai-Hangzhou High-speed Railway Company, in collaboration with China Railway Eleventh Bureau and a team of expert academicians, is meticulously evaluating the construction plans to safeguard the underwater segment’s progression.
Zhang Jintao, the project manager for the Jintang Undersea Tunnel, noted, “The maximum depth of the tunnel will reach 78 meters, with water pressure peaking at 8.4 bar, equivalent to nearly one ton of weight on an adult’s palm.” He elaborated that during the construction of the “buffer zone” for the underwater segment, the team is making targeted adaptations, focusing on the shield’s tail-brushing, slurry formulation, and tunneling posture control, significantly enhancing process management and gathering a wealth of data under various conditions to ensure the shield machine’s effectiveness during its underwater journey.
The Ningbo-Zhoushan Railway is a major project within China’s Medium- to Long-Term Railway Network Plan (2016-2030). Spanning 76.4 kilometers with a design speed of 250 kilometers per hour, this project will end the historical absence of railway access in the Zhoushan Archipelago. It will connect the city of Zhoushan, the only prefecture-level city in the Yangtze River Delta without high-speed rail, to the national railway network. This connection is poised to facilitate the integrated development of Ningbo and Zhoushan, contribute to the Belt and Road Initiative, and promote high-quality development across the Yangtze River Delta region.
