The reporter learned from China Railway Construction Corporation that on August 19th, China's independently developed underwater tunnel shield machine "Shenjiang No.1" completed the excavation task and successfully reached 106 meters below sea level, marking a new record for underwater excavation of China's large shield machine. The 13.69km long the Pearl River Mouth Tunnel is a control project of the whole Shenjiang Railway, which is constructed by the combination of "mining method+shield method". The "Shenjiang No.1" shield tunneling machine, with a diameter of 13.42 meters, excavated 3.59 kilometers from Dongguan towards Nansha, Guangzhou, passing through 13 different geological layers and 5 composite geological formations. The picture shows the inside of the shield section of the the Pearl River Estuary Tunnel. According to Li Bing, the project leader of China Railway 14th Bureau, the construction company, the lowest point of the tunnel shield section is 106 meters below the water surface of the the Pearl River Estuary, and the maximum water pressure is up to 1.06 MPa. The area equivalent to the size of the shield machine nail cover needs to bear 10.6 kg of pressure. There is no equivalent engineering experience and design standards for reference in China. In response to construction difficulties, the construction team has tailored the "Shenjiang No.1" shield tunneling machine, strengthened the research and application of intelligent construction technology, and focused on seven technological innovation research projects, including ultra-high water pressure, rapid replacement of long-distance hard rock excavation tools, and in-situ disassembly of underwater small space shield tunneling machines, to ensure safe and efficient excavation of shield tunneling machines in adverse geological sections with ultra-high water pressure, ultra large burial depth, and crack development. The Shenjiang Railway is an important component of China's "Eight Vertical and Eight Horizontal" high-speed railway network along the coast. The main line is 116 kilometers long, with a designed speed of 250 kilometers per hour, passing through five cities: Shenzhen, Guangzhou, Dongguan, Zhongshan, and Jiangmen. After the completion and opening of the line, it will realize the half-hour high-speed rail interconnection between Shenzhen Qianhai Free Trade Zone and Guangzhou Nansha Free Trade Zone, which has positive significance for further building the "Greater Bay Area on the track" and promoting the economic and social development of the Pearl River Delta. (New Society)