On November 20, as the "Shenwan No. 1" shield machine on the right line of the Guangzhou-Dongguan-Shenzhen project successfully completed segment assembly of 683 rings and advanced beyond 1,250 meters, it officially entered construction in the Xiwan sea area of Shenzhen. This marks that the "Shenwan No. 1" shield machine will undertake a long-distance crossing beneath the Xiwan sea area through complex strata, and the project has entered a critical construction phase.

The section from Shenzhen Airport to Gushu Working Shaft on the Jichang-Qianhai section of the Guangzhou-Dongguan-Shenzhen Intercity Railway, constructed by China Railway 14th Bureau Group, is a controlling project for the entire line. It uses two slurry balance shield machines for construction and will become China's longest subsea shield tunnel for an intercity railway upon completion. Once open to traffic, it will further enhance the functions of the Guangzhou-Dongguan-Shenzhen Intercity Railway and is of great significance for improving the intercity network of the Guangdong-Hong Kong-Macao Greater Bay Area and realizing integrated regional economic development.

The "Shenwan No. 1" shield machine now crossing beneath the Xiwan sea area will bore a long-distance single-head drive of 3.1 kilometers under the sea, with a maximum crown burial depth of 49 meters. This greatly increases risks such as shield chamber entry operations, main bearing seal failure, and tail grout leakage, which may affect shield tunneling and even lead to risks such as seawater intrusion. During tunneling, the shield machine also needs to pass through various complex strata, including soft soil, fault fracture zones, upper-soft-lower-hard strata, and slightly weathered hard granite, posing extremely high safety risks. In the initial section entering the sea, the geology is mainly completely and moderately weathered granite, with high clay and mineral impurity content in the strata. The ground softens upon contact with water and easily causes mud cakes on the cutterhead. At the same time, there are also difficulties in maintaining pressure due to air leakage and high risks in chamber entry operations, which affect shield tunneling.

To ensure the smooth crossing of the "Shenwan No. 1" shield machine beneath the Xiwan sea area, the project department formulated comprehensive special construction plans and emergency response plans, organized emergency drills for water and sand ingress during shield tunneling beneath the sea area, and improved the emergency response and rescue capabilities of all personnel. It also prepared a detailed and rigorous "Guidance Manual for Engineering Technology and Risk Control of Shield Tunneling Beneath the Xiwan Sea Area" and conducted technical briefings on the plans for all construction personnel. The project department invited internal and external experts for discussions and consultations on several occasions, fully conducted surveys of similar strata, and drew on experience from similar sea-crossing projects to analyze and judge the tunneling management of the project's sea section in advance.

To ensure normal tunneling of the shield machine while crossing beneath the Xiwan sea area, before the "Shenwan No. 1" shield machine crossed beneath the sea, a comprehensive inspection and replacement of cutters was carried out, cutter management was strengthened, and the frequency of cutter replacement was reduced. Comprehensive maintenance was also performed on the shield machine, supporting slurry separation equipment, battery locomotives, gantry cranes, and mixing stations to avoid abnormal shutdowns due to failures. A reference table for tunneling parameter control was formulated, and tunneling parameters were continuously optimized during the crossing. During the sea crossing, muck sample management was strictly implemented, with muck samples collected for each ring and tunneling parameters adjusted promptly according to stratum changes. Dedicated personnel were assigned to monitor and patrol the sea surface daily, and monitoring of segment crown settlement and segments in the tunnel of the sea construction section was strengthened to improve early warning and response capabilities for dangerous situations.

Up to now, the "Shenwan No. 1" shield machine has advanced 34 meters into the sea. The project department will further refine work measures, consolidate responsibilities, strengthen safety and quality management of sea-crossing construction, overcome difficulties, and safely and efficiently advance project construction to ensure the smooth completion of the crossing beneath the Xiwan sea area.