On June 23, at a depth of 102 meters beneath the seabed in the Pearl River Estuary Tunnel of the newly built Shenzhen–Jiangmen Railway (hereinafter referred to as the "Shenjiang Railway"), the "Shenjiang No. 1" shield tunneling machine safely advanced to ring 1720, successfully passing through 17 fault zones totaling 490 meters in length, marking important progress in the construction of China's deepest underwater tunnel, which is about to reach its lowest point at 106 meters below the seabed.

The 13.69-kilometer-long Pearl River Estuary Tunnel is a key controlling project of the Shenjiang Railway, with a maximum burial depth of 106 meters and a maximum water pressure equivalent to 10.6 kilograms of pressure on an area the size of a fingernail. It is China's underwater tunnel with the greatest burial depth and highest water pressure, and also the world's deepest subsea high-speed railway tunnel.

The "Shenjiang No. 1" shield tunneling machine has successively passed through 13 types of strata, 5 types of composite geology, and 17 fault zones, among which the fault zones and their branches span 490 meters, with the widest No. 15 fault zone being 32.5 meters wide and granite strength reaching up to 124.6 megapascals. Due to uneven rock strata, uneven hardness, great burial depth, and high water pressure, risks such as tunnel face collapse, accumulation and sluggish discharge in the front chamber of the shield machine, abnormal collision damage to cutters, jamming of the cutterhead, and failure of the tail seal are highly likely to occur during construction, requiring continuous construction and posing extremely great construction difficulties.

According to Li Bing, the on-site project manager of the China Railway 14th Bureau Group, the construction team strengthened the research, development, and application of intelligent construction technologies and adopted advanced geological forecasting technology to accurately detect and provide early warning of the geology within 100 meters ahead. "We developed and used new shield cutters and wear-resistant materials, installed a cutter wear monitoring system to monitor changes in parameters such as cutter temperature and rotational speed in real time, with autonomous pop-up alarms. Through the collection, analysis, assessment, instruction, and execution of key indicators, we accurately determine cutter wear conditions, achieving intelligent analysis, precise measures, and efficient tunneling."

According to reports, the "Shenjiang No. 1" shield tunneling machine is responsible for tunneling 3,590 meters from Dongguan toward Nansha, Guangzhou. After breaking through the fault zone section, it entered a relatively intact hard rock section and is currently tunneling toward 106 meters below the seabed.

It is understood that the Shenjiang Railway is an important component of the coastal corridor of China's "Eight Vertical and Eight Horizontal" high-speed railway main corridors. It is a major transportation infrastructure project serving the Belt and Road Initiative and supporting the construction of the Guangdong-Hong Kong-Macao Greater Bay Area and the China (Guangdong) Pilot Free Trade Zone. Once completed and opened to traffic, it will help create a half-hour living circle and economic circle in the Guangdong-Hong Kong-Macao Greater Bay Area, directly radiate and drive the coordinated regional development of eastern Guangdong, western Guangdong, and the Pearl River Delta, and enable half-hour high-speed rail connectivity between the Qianhai Pilot Free Trade Zone in Shenzhen and the Nansha Pilot Free Trade Zone in Guangzhou.