Deepest underwater tunnel construction reaches 106 meters below sea level

On August 19, the "Shenjiang No. 1" tunnel boring machine completed its mission at a depth of 106 meters beneath the Pearl River estuary, marking a new world record for underwater high-speed rail tunnel construction. The achievement was made as the Shenzhen-Jiangmen Railway's underwater tunnel reached its deepest point.

The 13.69-kilometer-long tunnel is a key component of the Shenzhen-Jiangmen Railway project and employs a combination of mining and shield tunneling techniques. The machine has dug a total of 3,590 meters from Dongguan towards Nansha in Guangzhou.

(Photo provided by China Railway Guangzhou Group)

During the digging process, the China Railway 14th Bureau Group Corporation Limited utilized a tunnel boring machine with a diameter of 13.42 meters, navigating beneath several main shipping routes while traversing 13 different strata and five types of complex geological conditions. Notably, it managed to progress through 2.75 kilometers of hard rock, with granite strength peaking at an impressive 124.6MPa.

According to Li Bing, the project manager from China Railway 14th Bureau Group Corporation Limited, the lowest point of the tunnel is located 106 meters below the surface of the Pearl River estuary. The "Shenjiang No. 1" machine can withstand water and soil pressure of up to 10.6 bar—equivalent to a 10.6 kg load on the size of a fingernail—with no comparable engineering experience or design standards available domestically.

(Photo provided by China Railway Guangzhou Group)

The tunnel boring machine began its journey in December 2021 and took 969 days to reach the remarkable depth. Chen Xingfei, the chief engineer of the project, highlighted that one of the most challenging segments involved navigating a 490-meter-long fault zone and branches, characterized by uneven rock layers and high water pressure, which posed significant risks during construction.

In response to these challenges, the project team enhanced their research and application of smart construction technologies, deploying cutting-edge tools such as wear monitoring systems, advanced geological forecasting technologies, and automated welding robots. Their innovative efforts have led to the filing of five invention patents and seven utility model patents, along with 17 published papers, contributing valuable insights for future projects in similar geological conditions.

(Photo provided by China Railway Guangzhou Group)

Situated in the heart of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA), the Shenzhen-Jiangmen Railway is a vital part of China's coastal high-speed rail network. Once operational, it will facilitate a half-hour transit zone between major economic hubs, connecting Shenzhen's Qianhai Free Trade Zone and Guangzhou's Nansha Free Trade Zone via high-speed rail, thereby enhancing regional connectivity and economic integration.

(cnbayarea.org.cn & GDToday)