On September 28, as the "Fenjin" shield machine successfully arrived at the receiving shaft, the south-line shield tunnel of the Zhuhai Tunnel Project TJ2 section undertaken by China Railway Tunnel Group—an underwater super-large-diameter cross-sea shield tunnel under construction in the Guangdong-Hong Kong-Macao Greater Bay Area—achieved breakthrough. Previously, the north-line shield tunnel of the project had already broken through first, and this breakthrough of the south-line shield tunnel marks the complete fulfillment of the project's dual-line shield tunneling task.

It is reported that the Zhuhai Tunnel Project alignment runs parallel to the south side of the Zhuhai Bridge, with a design of six lanes in both directions and a driving speed of 80 km/h, and a total length of about 5,000 meters. The civil works are divided into two sections, TJ1 and TJ2, for construction. After completion, the Zhuhai Tunnel and the Zhuhai Bridge will form a "bridge above, tunnel below" configuration connecting to Zhuhai Avenue, thereby alleviating traffic pressure on the Zhuhai Bridge and improving the quality and speed of east-west connectivity. In particular, when severe weather such as typhoons occurs, normal passage needs can be guaranteed. In the future, the Zhuhai Tunnel will become an all-weather lifeline corridor connecting the east and west districts of Zhuhai.

Along the Zhuhai Tunnel Project alignment, the TJ2 section undertaken by China Railway Tunnel Group is 3,800 meters long, with a shield section of 2,930 meters and an open-cut section of 870 meters, and a maximum burial depth of 35 meters. The project uses two super-large-diameter slurry balance shield machines with a diameter of 15.01 meters, the "Kaituo" and the "Fenjin." The two shield machines were tailor-made for the unique silty clay strata of the Zhuhai area, with basically identical relevant parameters: a total length of about 123 meters, a weight of about 4,200 tons, and a cutterhead weight of about 600 tons, with all technical indicators reaching world-leading levels. The two shield machines are arranged in parallel on the south side of the Zhuhai Bridge, tunneling from west to east, crossing the Modaomen waterway estuary of the Pearl River, and completing reception on the east bank of the bridge.

According to the introduction, the construction of this section mainly involves three major difficulties: First, tunneling in extremely soft shallow-cover strata. Large-diameter slurry shield construction in shallow-cover silty strata faces many challenges, such as difficulty in controlling shield attitude, susceptibility of the shield to roof collapse and slurry leakage, great difficulty in controlling segment uplift, and poor stability of the formed tunnel. Second, long-distance crossing of boulders and soft-over-hard strata. Such strata are characterized by high strength, long distance, uneven hardness, and difficulty in surveying; when the shield tunnels in soft-over-hard strata, it causes greater damage to the shield equipment, results in slow tunneling speed, and imposes high requirements on circulation control, with risks of stratum collapse, cutter eccentric wear, and seal damage. Third, the tunnel needs to pass beneath important structures and buildings on the east bank, and directly below the tunnel there is a structural fracture zone, which is prone to risks such as collapse and roof fall, placing extremely high demands on the level of shield tunneling control.

To overcome the engineering construction difficulties, the project team incorporated a series of innovative technologies such as automatic control and sensing during construction, achieving quality control throughout the entire construction process and fundamentally solving problems such as roof collapse and slurry leakage, great difficulty in controlling segment uplift, and poor stability of the formed tunnel; it used a self-developed front-mounted atmospheric cutter-changing cutter barrel and a cutter monitoring and protection system, effectively solving problems such as abnormal damage to the atmospheric cutter-changing barrel, inaccurate monitoring, and cutters retreating and falling off, improving the tunneling efficiency and safety of the shield machine, and avoiding risks such as stratum collapse, cutter eccentric wear, and seal damage; it also researched and summarized a set of construction methods for super-large-diameter slurry shield tunneling in extremely soft shallow-cover silty strata, improving the tunneling efficiency of super-large-diameter slurry shields. 

After completion, the Zhuhai Tunnel Project will connect to Zhuhai Avenue. Zhuhai Avenue is regarded as Zhuhai's "golden central axis," leading the city westward, driving the upgrading of industries and economic development along the route, with the city center and population shifting accordingly. It not only breaks down geographical barriers and promotes economic exchange and development between regions, but has also become an important artery for Zhuhai's urban development, playing an irreplaceable role in advancing Zhuhai's urbanization and modernization process.