On August 23, the domestically made "Shenjiang No. 1" slurry shield tunneling machine rolled off the production line in Changsha. The machine is 130 meters long, weighs 3,300 tons in total, and has an excavation diameter of 13.42 meters. It will be used in the Pearl River Estuary Tunnel project of the newly built Shenzhen-Jiangmen High-Speed Railway (referred to as the "Shenjiang High-Speed Railway"), a major transportation infrastructure project in the Guangdong-Hong Kong-Macao Greater Bay Area.

"Shenjiang No. 1" is the first domestically made shield tunneling machine used for high-speed rail subsea tunnel construction. Its cutterhead is painted with "awakening lion" elements to highlight Guangdong's regional cultural characteristics. It was jointly developed by China Railway 14th Bureau Group and China Railway Construction Heavy Industry Group, has independent intellectual property rights, and adopts multiple world-first technologies.

The Pearl River Estuary Tunnel used for construction is located at the Pearl River estuary between Dongguan and Guangzhou. It has a total length of 13.69 kilometers, with an offshore section about 11.05 kilometers long. The shield-driven section has a maximum burial depth of 106 meters and a maximum water pressure of 1.06 MPa, making it currently China's subsea tunnel with the greatest burial depth and highest water pressure and a key control project of the Shenjiang High-Speed Railway. Changing cutters under the seabed in an ultra-high water pressure environment places very high demands on the performance of the shield tunneling machine.

The Pearl River Estuary Tunnel is a long-distance tunnel in composite strata under ultra-high water pressure, with extremely complex geological conditions, many environmentally sensitive points, and relatively severe corrosiveness of the surrounding water environment. During excavation, the shield tunneling machine must safely pass through multiple fault fracture zones, bedrock protrusions, and various composite strata such as mixed hard and soft ground. "After completing the excavation task, the shield tunneling machine will be dismantled in situ inside the tunnel, and the machine's integrity rate must be ensured," said Li Bing. This construction method is the first of its kind in China and poses new challenges for dismantling and transportation.

In response to the difficulties of subsea tunnel construction such as ultra-high water pressure, ultra-hard rock strata, continuous crossing of fault fracture zones, and strong seawater corrosiveness, the development team carried out targeted designs for the shield tunneling machine. Targeted research and design were conducted on the cutterhead structure, cutter types, drive seals, shield shell design, slurry circulation mucking, pressure resistance, and corrosion resistance. The final "Shenjiang No. 1" is equipped with a conventional pressurized heavy-duty composite cutterhead, a retractable main drive, and a double-layer shell. It also integrates a series of intelligent systems, including high-precision large-flow slurry circulation, efficient heavy-load material transport, automatic pressurization of main drive seals, synchronous single-fluid and dual-fluid grouting, shield tail clearance measurement, automatic segment selection and floating detection, and tunnel ventilation and cooling.

The successful research, development, and manufacturing of the "Shenjiang No. 1" shield tunneling machine marks an important stage in the entry of the Shenjiang Railway Pearl River Estuary Tunnel into shield construction. Next, the machine will be dismantled after rolling off the production line and transported to the construction site for full-system assembly and commissioning, ensuring early launch and excavation so that China's high-speed rail can speed beneath the seabed at a depth of 100 meters.

Industry experts believe that once completed, the Pearl River Estuary Tunnel project will become another world-class mega project and will accumulate technology and provide valuable experience for subsea tunnel construction worldwide.

The Shenjiang High-Speed Railway is located in the center of the Guangdong-Hong Kong-Macao Greater Bay Area. Its main line has a total length of 116.12 kilometers and a design speed of 250 kilometers per hour, while the Pearl River Estuary Tunnel is designed for 200 kilometers per hour. It is an important part of the coastal corridor of the national "eight vertical and eight horizontal" high-speed railway network and is expected to be completed and opened to traffic in 2025. Once completed and opened, it will directly drive and promote the coordinated regional development of eastern Guangdong, western Guangdong, and the Pearl River Delta, and the Qianhai Free Trade Zone in Shenzhen and the Nansha Free Trade Zone in Guangzhou will achieve half-hour high-speed rail connectivity.