On the morning of May 28, 2022, China Railway 14th Bureau Shenjiang No. 1 shield machine was excavated to the 200th ring, with a total of 400 meters of excavation, marking the official transfer of the first bid section of the new Pearl River Mouth Tunnel of the Shenjiang Railway from the shield test excavation to full speed. The excavation mode is about to start a journey through the sea.

Jia Wenxian, Shield Manager of the Project Department of China Railway 14th Bureau, introduced that Shenjiang No. 1 shield machine was excavating from Humen, Dongguan to Nansha, Guangzhou. After nearly two months of overall running-in of personnel and all elements of the shield machine, it now maintains an average of 5 excavations per day. The speed of the ring reaches the design capacity. The project department has continuously overcome two major risk sources of the shield machine starting and the upper soft and lower hard strata in the test section, which is still 200 meters away from the shield excavation into the sea.

According to Li Bing, the person in charge of the Shenjiang Railway Project of the China Railway 14th Bureau, the Pearl River Mouth Tunnel, with a total length of 13.69 kilometers, is a key control project of the Shenjiang Railway. It is a single-hole double-track high-speed railway with a design speed of 200 kilometers per hour. The hydrology and geology of the tunnel project are extremely complex. There are many main waterways under the tunnel, and the surrounding environment is more corrosive. The maximum depth of the tunnel is 106 meters, and the sea water pressure is 10.6 bar, which is equivalent to the size of a fingernail. The area bears 10.6 kilograms of pressure. The high water pressure construction area is about 110 meters. It is the underwater tunnel with the largest buried depth and the highest water pressure in China. The maximum water pressure of the shield section is the highest in the world.

The total length of the tunnel for the first bid section constructed by the China Railway 14th Bureau is 4,515 meters. The shield excavation diameter is 13.42 meters, the outer diameter of the segment is 12.9 meters, the inner diameter is 11.7 meters, and the segment ring width is 2 meters. The tunnel passes through 5 kinds of composite geology, 13 kinds of strata, and 17 fault zones, of which the full-section hard rock is 2.75 kilometers long, and the rock strength is up to 124.6 MPa. It is one of the most difficult underwater tunnels under construction in China.

The main line of the Shenjiang Railway has a total length of 116.1 kilometers and passes through 5 cities including Shenzhen, Guangzhou, Dongguan, Zhongshan and Jiangmen. The estimated total investment of the project is 51.31 billion yuan, the design speed is 250 kilometers per hour, and the construction period is 5.5 years. The Shenjiang Railway is an important part of the coastal channel of China's eight vertical and eight horizontal high-speed rail network. After the completion and opening to traffic, the Qianhai Free Trade Zone in Shenzhen and the Nansha Port Free Trade Zone in Guangzhou will achieve a half-hour high-speed rail interconnection.Editor/Ma Xue