China's deepest undersea high-speed railway tunnel has reached a record excavation depth of 113 meters beneath the seabed, marking a major milestone in the construction of the Shenzhen-Jiangmen High-Speed Railway.

The Shenzhen-Jiangmen railway, linking the southern cities of Shenzhen and Jiangmen, is a vital component of the coastal high-speed rail corridor. The project has now entered a critical phase of construction.

At the heart of the project is the Pearl River Estuary Tunnel, an undersea shield tunnel. During the Qingming Festival holiday, construction workers remained on duty as China's domestically developed large-diameter tunnel boring machine (TBM), "Shenjiang-1," continued round-the-clock excavation.

After more than four years of continuous work, the TBM has advanced over 4 kilometers and reached a depth of 113 meters underwater, setting a new world record for the deepest undersea high-speed rail shield tunnel. The tunnel's maximum depth will reach 116 meters, where water pressure poses significant engineering challenges.

Geological conditions along the route are highly complex. The TBM must pass through 13 strata, five composite geology types, and six fault zones. Resembling a "steel dragon," the machine features a massive rotating cutterhead at the front, equipped with densely packed cutting tools that crush rock and soil as it moves forward.

The TBM operates with two main pipeline systems. One delivers fluid slurry to the cutterhead to reduce friction, and the other transports thick, debris-laden slurry back to the surface for treatment. At the processing plant, excavated materials are separated, and the treated slurry is recycled for reuse.

Behind the cutterhead, workers assemble precast concrete segments to form the tunnel lining. Each segment is about two meters wide, and nine segments are needed to complete a full ring for the tunnel, which has a diameter exceeding 13 meters. This simultaneous excavation and assembly method helps significantly improve construction efficiency.

The Pearl River Estuary Tunnel, stretching 13.69 kilometers, is a critical section of the railway. Located between Dongguan and Guangzhou, the tunnel crosses multiple waterways at the mouth of the Pearl River.

The Shenzhen-Jiangmen High-Speed Railway runs 116 kilometers from Shenzhen's Xili area in the east to Jiangmen in the west. Once completed, travel time between the two cities will be reduced to under one hour.

The project is expected to further enhance the rail network in the Guangdong-Hong Kong-Macao Greater Bay Area, improving regional connectivity and supporting economic integration.