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].

Core Points - The Ningbo-Zhoushan Railway's underwater tunnel, known as the Jintang Submarine Tunnel, is a record-breaking engineering project, measuring 16.18 kilometers in total length, with an underwater section of 11.21 kilometers and a maximum depth of 78 meters, making it the world's longest underwater high-speed rail tunnel [2][3] - The construction employs two shield machines that start from both Ningbo and Zhoushan sides, advancing towards each other while navigating high water pressure and complex geological conditions [2] - The project is significant for the integration of the Yangtze River Delta region, as it will end the historical lack of railway access to Zhoushan upon completion in late 2026 [7] Construction Details - As of May 2024, the shield machine has advanced nearly 2,400 meters, currently located about 65 meters below sea level, marking a critical phase as it transitions from land to marine construction [3] - The shield machine must traverse various geological layers, including 4 segments of soft soil and 8 segments of hard rock, with hard rock layers comprising nearly 70% of the total [3] - Advanced technologies, such as a proactive geological forecasting system, are utilized to enhance the precision of geological assessments and improve construction safety [5] Workforce and Project Management - The project employs over 200 workers who operate in two shifts around the clock to ensure continuous progress [7] - The project team is committed to maintaining high-quality standards and timely completion, aligning with the goals of the 14th Five-Year Plan [7]

Core Points - The Ningbo-Zhoushan Railway's Jintang underwater tunnel is a record-breaking engineering project, measuring 16.18 kilometers in total length, with an underwater section of 11.21 kilometers and a maximum depth of 78 meters, making it the world's longest underwater high-speed rail tunnel [1][2] - The construction employs two shield machines that start from both Ningbo and Zhoushan sides, facing complex geological conditions, including high water pressure and various soil types [1][2] - The project utilizes advanced technologies, such as a proactive geological forecasting system, to enhance construction efficiency and safety [3] Group 1 - The Jintang underwater tunnel is a key project for the Ningbo-Zhoushan Railway, with significant implications for regional connectivity and economic development [1][3] - The shield machine, named "Yongzhou," has already progressed nearly 2400 meters since its launch in May 2024, marking a critical milestone as it transitions from land to underwater construction [2] - The project team has designed the shield machine's cutter head to withstand the challenges posed by alternating soft and hard soil layers, which constitute nearly 70% of the tunnel's path [2][3] Group 2 - The construction site employs over 200 workers who operate in two shifts around the clock, aiming for high-quality and timely project completion by the end of 2026 [3] - The successful completion of the Jintang underwater tunnel will end the historical lack of railway connectivity to Zhoushan, contributing to the high-quality integration of the Yangtze River Delta region [3]

Core Insights - The successful crossing of the sea embankment by the "Yongzhou" shield machine marks the full commencement of the world's longest underwater high-speed rail tunnel construction [1] Group 1: Project Overview - The Jintang underwater tunnel, located between Ningbo and Zhoushan, has a total length of 16.18 kilometers and utilizes two shield machines for simultaneous excavation and connection underwater [1] - The underwater section of the tunnel is 11.21 kilometers long, with a maximum burial depth of 78 meters, and the construction is expected to take three years [6] Group 2: Technological Innovations - The "Yongzhou" shield machine is equipped with advanced technologies such as a rolling cutter wear monitoring system and a geological forecasting system to handle complex geological conditions [2][3] - The number of rolling cutters on the "Yongzhou" shield machine has been increased to 300, enhancing its rock-breaking capability and wear resistance [2] - A digital shield system allows for remote operation and real-time monitoring of the shield machine's parameters, improving safety and efficiency during construction [4] Group 3: Specialized Techniques - Saturated diving technology is employed for high-pressure tool replacement, allowing divers to work for up to 28 days under high pressure, which is essential for the maintenance of the shield machine [6] - The project has established multiple research topics focused on enhancing performance in complex geological and marine environments, resulting in several innovative tools and methods [6]