Jintang undersea tunnel for Yongzhou (Ningbo-Zhoushan) high-speed railway under construction

Technicians work at an operation room for "Yongzhou" tunnel boring machine at the construction site of Jintang undersea tunnel in east China's Zhejiang Province, Sept. 22, 2025. The self-developed tunnel boring machine "Yongzhou" achieved a tunneling mileage exceeding 2,470 meters on Monday at a depth of 65 meters below sea level of Jintang waterway between cities of Ningbo and Zhoushan in east China's Zhejiang Province. The milestone marks the completion of over half of the tunneling work in Ningbo section of Jintang undersea tunnel. (Xinhua/Huang Zongzhi)

The tunnel, stretching 16.18 km, is an important facility for the Yongzhou (Ningbo-Zhoushan) high-speed railway and is set to be the world's longest undersea railway tunnel upon completion. 

Technicians conduct remote construction management of Jintang undersea tunnel via a smart monitoring platform in Ningbo, east China's Zhejiang Province, Sept. 22, 2025. The self-developed tunnel boring machine "Yongzhou" achieved a tunneling mileage exceeding 2,470 meters on Monday at a depth of 65 meters below sea level of Jintang waterway between cities of Ningbo and Zhoushan in east China's Zhejiang Province. The milestone marks the completion of over half of the tunneling work in Ningbo section of Jintang undersea tunnel. (Xinhua/Huang Zongzhi)

"Yongzhou" tunnel boring machine operates at the construction site of Jintang undersea tunnel in east China's Zhejiang Province, Sept. 22, 2025. The self-developed tunnel boring machine "Yongzhou" achieved a tunneling mileage exceeding 2,470 meters on Monday at a depth of 65 meters below sea level of Jintang waterway between cities of Ningbo and Zhoushan in east China's Zhejiang Province. The milestone marks the completion of over half of the tunneling work in Ningbo section of Jintang undersea tunnel. (Xinhua/Huang Zongzhi)

This photo shows the construction site of Jintang undersea tunnel at a depth of 52 meters below sea level in east China's Zhejiang Province, Sept. 22, 2025. The self-developed tunnel boring machine "Yongzhou" achieved a tunneling mileage exceeding 2,470 meters on Monday at a depth of 65 meters below sea level of Jintang waterway between cities of Ningbo and Zhoushan in east China's Zhejiang Province. The milestone marks the completion of over half of the tunneling work in Ningbo section of Jintang undersea tunnel. (Xinhua/Huang Zongzhi)

Technicians conduct remote construction management of Jintang undersea tunnel via a smart monitoring platform in Ningbo, east China's Zhejiang Province, Sept. 22, 2025. The self-developed tunnel boring machine "Yongzhou" achieved a tunneling mileage exceeding 2,470 meters on Monday at a depth of 65 meters below sea level of Jintang waterway between cities of Ningbo and Zhoushan in east China's Zhejiang Province. The milestone marks the completion of over half of the tunneling work in Ningbo section of Jintang undersea tunnel. (Xinhua/Huang Zongzhi)

A technician works inside "Yongzhou" tunnel boring machine at the construction site of Jintang undersea tunnel in east China's Zhejiang Province, Sept. 22, 2025. The self-developed tunnel boring machine "Yongzhou" achieved a tunneling mileage exceeding 2,470 meters on Monday at a depth of 65 meters below sea level of Jintang waterway between cities of Ningbo and Zhoushan in east China's Zhejiang Province. The milestone marks the completion of over half of the tunneling work in Ningbo section of Jintang undersea tunnel. (Xinhua/Huang Zongzhi)

A worker replaces tail seal grease for "Yongzhou" tunnel boring machine at the construction site of Jintang undersea tunnel in east China's Zhejiang Province, Sept. 22, 2025. The self-developed tunnel boring machine "Yongzhou" achieved a tunneling mileage exceeding 2,470 meters on Monday at a depth of 65 meters below sea level of Jintang waterway between cities of Ningbo and Zhoushan in east China's Zhejiang Province. The milestone marks the completion of over half of the tunneling work in Ningbo section of Jintang undersea tunnel. (Xinhua/Huang Zongzhi)