Core Insights - The "Yongzhou" shield machine has achieved over half of its tunneling progress for the world's longest underwater high-speed rail tunnel, marking a significant milestone in the construction of the Ningbo-Zhoushan railway [1][3]. Group 1: Project Overview - The Jintang underwater tunnel is a key project of the Yongzhou railway, stretching 16.18 kilometers, with the shield section measuring 11.21 kilometers [3]. - The tunnel employs two shield machines, "Yongzhou" and "Dinghai," which are advancing simultaneously from both Ningbo and Zhoushan sides [3]. Group 2: Technical Challenges - The geological conditions along the Jintang underwater tunnel are extremely complex, requiring the crossing of various risk sources such as sea dikes, docks, and shipping lanes [4]. - The maximum depth of the underwater section reaches 78 meters, with a maximum water pressure of 8.4 bar, equivalent to nearly 1 ton of weight on an adult's palm [4]. - The Ningbo side has experienced frequent geological changes, necessitating high-pressure tool changes, with the "Yongzhou" machine completing 12 geological transitions and changing tools over 2400 times [4]. Group 3: Strategic Importance - The Yongzhou railway is a major project in China's Medium- and Long-term Railway Network Plan (2016-2030), with a total length of 76.4 kilometers and a design speed of 250 kilometers per hour [4]. - Once operational, the project will connect Zhoushan, the only city in the Yangtze River Delta without a railway, to the national railway network, significantly enhancing regional integration and development [4].