On August 19, at the construction site of the Pearl River Estuary Tunnel of the Shenjiang Railway, the deepest submarine tunnel shield machine "Shenjiang No. 1" jointly built by China Railway Construction Heavy Industry and China Railway 14th Bureau successfully reached 106 meters under the seabed and completed the established 3590-meter excavation task, which is the deepest record of underwater excavation of China's shield machine and the deepest record of China's high-speed rail shield tunnel.

The "Shenjiang No. 1" shield machine reached the seabed at 106 meters

With a total length of 13.69 kilometers, the Pearl River Estuary Tunnel is a key control project of the Shenzhen-Jiangxi Railway. The "Shenjiang No. 1" shield machine excavated 3,590 meters from Dongguan to Nansha, Guangzhou. In the process of tunneling, the shield machine passed through a number of main channels, successively crossed 13 kinds of strata, 5 kinds of composite geology, the full-section hard rock excavation is up to 2.75 kilometers, the strength of granite is up to 124.6 megapascals, and it also crosses 17 fault zones and branches in a row, and the complex hydrological and geological conditions of the interval project have brought great difficulty to the project.

Schematic diagram of the tunnel profile

The lowest point of the shield section of the tunnel is located 106 meters below the water surface of the Pearl River Estuary, which is equivalent to the pressure of 10.6 kg on an area the size of a fingernail.

The "Shenjiang No. 1" shield machine rolled off the assembly line in China Railway Construction Heavy Industry

In view of the construction problems, the "Shenjiang No. 1" shield machine is equipped with a series of intelligent systems such as normal-pressure heavy-duty composite cutterhead, high-load main drive, synchronous single-liquid and double-liquid grouting, etc., with a maximum pressure bearing capacity of 12bar, which greatly improves the adaptability under ultra-high water pressure conditions on the seabed and ensures that the shield machine excavates continuously, stably and safely in the poor geological sections with ultra-high water pressure, large buried depth and fracture development.

Located in the center of the Guangdong-Hong Kong-Macao Greater Bay Area, the Shenzhen-Jiangxi Railway is an important part of the coastal passage of the national "eight vertical and eight horizontal" high-speed railway network.