A silent "underground passage" is quietly rewriting the world tunnel engineering record 109 meters below the choppy sea surface of the the Pearl River Estuary in China. On January 6, 2025, as the "Shenjiang No.1" shield machine completed the assembly of the 2000th ring segment, the Humen section of the Pearl River Mouth Tunnel of Shenjiang Railway, which was constructed by China Railway 14th Bureau, successfully broke the 4000 meter barrier. This 13.69 kilometer long tunnel is not only the deepest underwater high-speed rail shield tunnel in the world today, but also a focus of attention in the international engineering community due to its passage through extremely complex geological conditions.

World class construction challenges

As the most critical "choke" project of the whole Shenjiang Railway, the the Pearl River Estuary Tunnel is constructed by the combined construction method of "shield at both ends+middle mine", with the design standard and construction difficulty reaching the world's top level. The shield tunnel section is excavated from Humen, Dongguan to Nansha, Guangzhou, with a one-way length of 5360 meters and a maximum burial depth of 116 meters below sea level. It is subjected to a water pressure of up to 12.5 atmospheres, equivalent to over 120 tons of pressure per square meter.

The complexity of geological conditions can be called a 'geological museum'. The project requires crossing 15 different geological layers, 6 composite geological conditions, and 35 fault zones. The full section of hard rock is 2.75 kilometers long, and the highest compressive strength of granite reaches 124.6 megapascals, which is more than 6 times the strength of ordinary concrete. The total length of the fault zone and branch sections is 490 meters, and the widest fault zone, No.15, has a width of 32.5 meters. These geological conditions have brought unprecedented challenges to the construction. Especially in the second stage of excavation, the dense and continuous F2 fault zone stretches for 237 meters, with strong water content and high quartz content of schist and granite, posing a severe challenge to the shield tunneling tools.

Intelligent equipment overcomes underwater obstacles

Faced with such a complex geological environment, the project team demonstrated the innovative strength of Chinese engineering technology. The "Shenjiang No.1" shield tunneling machine, with a total weight of 3800 tons and a length of 130 meters, is a specially designed super equipment for this project. Its excavation diameter reaches 13.42 meters, equivalent to the height of a four story building. In the completed first 3590 meter excavation, the shield machine set a new record for underwater shield tunneling in China.

To cope with more complex geological conditions in the future, the project team conducted a comprehensive survey, evaluation, and maintenance renovation of the shield machine at a depth of 100 meters underwater. Li Bing, the on-site manager of China Railway 14th Bureau, introduced that the team has focused on improving the pressure holding system and cutterhead wear resistance of the shield machine, ensuring stable operation of the equipment in high-pressure and rich water environments. At the same time, the project adopts advanced geological forecasting technology, which can accurately detect the geological conditions within a hundred meters ahead and provide timely warnings. The installed tool wear monitoring system achieves real-time monitoring of the status of shield tunneling tools, providing technological support for safe and efficient excavation.

These technological innovations not only solve the technical problems of the project itself, but also accumulate valuable experience for China to construct underwater tunnels under complex geological conditions. Especially in the technical practice of maintaining and renovating shield tunneling equipment in environments with large burial depths and high water pressure, it has filled the technical gap in related fields in China.

Accelerate the integration process of the Greater Bay Area

As an important component of China's "Eight Verticals and Eight Horizontals" high-speed railway network along the coast, the Shenjiang Railway has a total length of 116.309 kilometers and seven stations including Xili, Shenzhen Airport East, Binhai Bay, Nansha, Zhongshan North, Henglan, and Jiangmen. The designed speed is 200-250 kilometers per hour. Binhai Bay Station, located in Humen Road East Community, with a building area of 17998 square meters, will become an important transportation hub connecting the east and west sides of the the Pearl River Estuary.

The construction progress of the the Pearl River Estuary Tunnel is directly related to the opening time of the whole Shenjiang Railway. After the completion of the railway, it will achieve high-speed rail interconnection between Shenzhen Qianhai Free Trade Zone, Dongguan Binhai Bay New Area, and Guangzhou Nansha Free Trade Zone, forming a fast rail transit corridor connecting the core areas of the Guangdong Hong Kong Macao Greater Bay Area. The travel time from Humen to Nansha, Zhongshan, Jiangmen, western Guangdong, Guangxi and other places in Guangzhou will be significantly shortened, effectively promoting the free flow of talents, capital, information and other factors within the Greater Bay Area. Keywords: traffic news, traffic news information

More profoundly, this project reflects China's comprehensive strength in the field of super engineering. From equipment manufacturing to construction technology, from geological exploration to risk management and control, the whole process of the Pearl River Estuary Tunnel Project shows the advanced level of China's infrastructure construction. With the continuous progress of tunnel excavation, the "Great Bay Area on the Track" is changing from a blueprint to a reality, and the the Pearl River Estuary Graben will become a thoroughfare, providing a solid transportation support for the Guangdong Hong Kong Macao Great Bay Area to build a world-class urban agglomeration. This world-class project is not only a victory in technological challenges, but also a concrete practice of the national strategy of regional coordinated development, indicating that the integration process of the Guangdong Hong Kong Macao Greater Bay Area will enter a new acceleration stage. (This article is from the official website www.seetao.com of Jian Dao. Reproduction without permission is prohibited, otherwise it will be prosecuted. Please indicate Jian Dao website+original link when reprinting.) Jian Dao website traffic column editor/Gao Xue