On August 25, the "Greater Bay Area" shield tunneling machine, jointly developed by China Railway Engineering Equipment Group and China Railway Tunnel Group for China's deepest underwater tunnel—the Pearl River Estuary Tunnel on the Shenzhen-Jiangmen Railway—rolled off the production line in Shunde, Guangdong. It will next be disassembled and transported to the construction site. The "Greater Bay Area" has an excavation diameter of 13.32 meters, a total length of 133 meters, and a total weight of about 3,900 tonnes.

The Shenzhen-Jiangmen Railway is an important part of the coastal corridor of the national "eight vertical and eight horizontal" high-speed rail main network, with a main line length of about 116 kilometers. The Pearl River Estuary Tunnel is 13.69 kilometers long, designed for a speed of 250 kilometers per hour, with a maximum underwater depth of 115 meters.

According to reports, during construction, builders will comprehensively apply the two main current tunnel construction methods—shield tunneling and the mining method. The ultra-high water pressure in the Pearl River Estuary Tunnel has no equivalent engineering precedent in China. In addition, the two shield tunneling machines must achieve precise breakthrough after long-distance underwater excavation, placing extremely high demands on dynamic construction control.