On August 9, at the Pearl River Estuary Tunnel of the Shenzhen-Jiangmen Railway—China's deepest subsea tunnel—the super-large-diameter shield tunneling machine "Greater Bay Area" (Dawanqu), operated by China Railway Tunnel Group, was the first to complete all 1,468 rings of excavation, reaching the designated mileage. This marks major progress in the construction of the entire Shenzhen-Jiangmen Railway.

The Shenzhen-Jiangmen Railway is an important component of the coastal corridor of the national "Eight Vertical and Eight Horizontal" high-speed rail network, and a major transportation infrastructure project for implementing the national strategy of developing the Guangdong-Hong Kong-Macao Greater Bay Area. The main line is 116 kilometers long, with a design speed of 250 kilometers per hour, passing through five cities: Shenzhen, Guangzhou, Dongguan, Zhongshan, and Jiangmen. Because the route needs to cross the Pearl River estuary between Guangzhou and Dongguan, where geological and hydrological conditions are extremely complex, the design scheme went through several comparisons and selections, and was ultimately changed from a combined road-rail bridge to an undersea tunnel.

The super-large-diameter shield tunneling machine "Greater Bay Area" was the first to complete its excavation task.

As a controlling project of the entire line, the Pearl River Estuary Tunnel of the Shenzhen-Jiangmen Railway is 13.69 kilometers long and uses two shield tunneling machines excavating toward each other. The shield-method tunnel in Section 2 is 2,930 meters long, with a maximum underwater burial depth of 115 meters and a maximum water pressure of up to 1.06 MPa, setting a record for the deepest subsea railway tunnel in China. The project construction faces three global challenges: ultra-long distance, ultra-high water pressure, and complex geology.

According to reports, Section 2 of the Pearl River Estuary Tunnel of the Shenzhen-Jiangmen Railway is 9.175 kilometers long in total and is an ultra-long subsea tunnel. The shield machine needs to carry out long-distance blind-end excavation in hard rock geology. The maximum water pressure is as high as 1.06 MPa, equivalent to bearing a weight of 10.6 kilograms on an area the size of a fingernail, with an intensity exceeding 10 standard atmospheres. There is no engineering experience or design standard under equivalent conditions in China for reference. The tunnel's geological conditions are extremely complex, with highly variable and changeable lithology, posing enormous challenges to equipment performance and construction technology.

The "Greater Bay Area" slurry balance shield tunneling machine has a diameter of 13.32 meters. It can not only withstand a maximum water pressure of 1.2 MPa, but is also supported by multiple innovative technologies, including a small cutter-spacing atmospheric composite cutterhead, a retractable main drive, ultra-high-pressure automatic compensation, a four-circuit pressure-maintenance system, and an air-cushion direct-discharge excavation system, ensuring continuous, stable, and safe excavation by the shield machine in unfavorable geological sections with ultra-high water pressure.

During project construction, the builders actively explored practical paths for intelligent construction of shield tunnels, equipped with China's first shield intelligent excavation system applied in a process-based manner, and applied an intelligent shield tunnel construction system centered on "Eight Intelligences."

Up to now, the Pearl River Estuary Tunnel of the Shenzhen-Jiangmen Railway has completed two-thirds of its overall construction task. After the Shenzhen-Jiangmen Railway is completed and opened to traffic, it will more closely connect the five Greater Bay Area cities of Shenzhen, Dongguan, Guangzhou, Zhongshan, and Jiangmen.