On August 19, China's independently developed undersea tunnel boring machine "Shenjiang No. 1" completed its excavation mission and successfully reached 106 meters below sea level. This also marks that China's large shield machine has set a new record for underwater excavation.
The 13.69-kilometer-long Pearl River Estuary Tunnel is a key project of the entire Shenzhen-Jiangmen Railway. It is constructed using a combination of "mining method + shield method". The "Shenjiang No. 1" shield machine with an excavation diameter of 13.42 meters excavated 3.59 kilometers from Dongguan to Guangzhou Nansha, crossing 13 types of strata and 5 types of composite geology.
According to the project manager of the construction unit China Railway 14th Bureau, the lowest point of the tunnel shield section is located 106 meters below the water surface of the Pearl River Estuary, and the maximum water pressure is as high as 1.06 MPa, which is equivalent to the shield machine having to withstand a pressure of 10.6 kilograms on an area the size of a fingernail. There is no engineering experience and design standards with equivalent conditions available for reference in China.
In response to construction difficulties, the construction team customized the "Shenjiang No. 1" shield machine, strengthened the research and development and application of intelligent construction technology, and concentrated on seven scientific and technological innovation research projects, including ultra-high water pressure, rapid replacement of long-distance hard rock tunneling tools, and in-situ disassembly of small-space submarine shield machines, to ensure the safe and efficient excavation of the shield machine in unfavorable geological sections with ultra-high water pressure, ultra-large burial depth, and developed cracks.
The Shenzhen-Jiangmen Railway is an important part of the coastal corridor of China's "eight vertical and eight horizontal" high-speed railway network. 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 line is completed and opened to traffic, it will realize the half-hour high-speed rail interconnection between the Shenzhen Qianhai Free Trade Zone and the Guangzhou Nansha Free Trade Zone, which will have positive significance for further building a "Greater Bay Area on Track" and promoting the economic and social development of the Pearl River Delta.