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On April 23, the cutterhead of the "Fenjin" (Striving Forward) shield machine successfully arrived at the receiving shaft in the Lüboyuan shield-driven section, the core section of the Nanjing Qiuteng–Wangjiang 220 kV line project, which is being built by State Grid Nanjing Power Supply Company and constructed by China Railway 14th Bureau Group, marking a further step toward full-line breakthrough for the project.

The Nanjing Qiuteng–Wangjiang 220 kV line project is one of the representative projects of Nanjing's "Double Hundred Action." It starts at the 500 kV Qiuteng Substation in Pukou District and ends at the 220 kV Wangjiang Substation in Jianye District, with a newly built line length of 27.91 km. The Lüboyuan shield-driven section is the core section for achieving full-line connectivity of the line. It is 568 m long, begins at the shield launching shaft on the west side of Wangjiang Substation, runs northwest to the shield receiving shaft, has a minimum turning radius of 200 m and a maximum cover depth of only 14.7 m, with segment outer diameter of 3.5 m, and is excavated using a slurry shield machine with an excavation diameter of 3.74 m.

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To ensure safe and smooth shield tunneling, State Grid Nanjing Power Supply Company and the China Railway 14th Bureau project construction team held multiple expert meetings to demonstrate and verify the shield machine selection, strengthen supporting equipment for shield tunneling, and formulate targeted plans for the application of new technologies, split launching of the shield, and shield tunneling. Affected by hydrological and stratum conditions, the project team adopted steel sleeve launching and receiving, and the shield machine passed in and out of the shaft through glass fiber reinforcement, which can greatly reduce the risk of water leakage during shield launching and receiving. To solve the difficulty of muck transport, the project introduced a rotary bucket excavator to break up and dissolve the muck in slurry and use tank trucks for wet removal, thereby resolving the construction impact caused by muck transport and ensuring continuous shield tunneling. Since the "Fenjin" shield machine was launched earlier this year, the project team has successfully overcome multiple challenges, including launching and receiving within the steel sleeve, secondary shutdown and pressure maintenance during split launching of the shield machine, and small-curvature turning radius. It has smoothly passed beneath a large-diameter sewage pipe, a large-section sewage box culvert, and an existing abutment, maintaining a construction record of 18 rings of tunneling per day.

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To ensure the quality of the formed tunnel, the project construction team strengthened technological innovation. Relying on the engineering project, they actively carried out the research topic "Research on Key Technologies of Socket-Type Segments for Power Shield Tunnels," promoting the successful implementation of the new "socket-type segment" technology. This effectively improved the structural stress performance, waterproof performance, and appearance quality of the formed tunnel, reduced the difficulty and cost of later operation, and also provided an important reference and basis for the construction of similar power tunnel projects in the future. In addition, they optimized the installation method of cable trays by using embedded sleeves on the inner curved surface of the socket-type segments to install tunnel cable supports, which not only avoided damage to the segment body but also reduced the construction risk of welding operations inside the tunnel.

It is understood that after the tunnel breakthrough, the follow-up work of dismantling the shield machine will be carried out at full speed to ensure the project milestone objectives are achieved. After the project is fully put into operation, green wind power from northern Jiangsu can be transmitted directly through the existing "cross-river main trunk" of the Nanjing Yingtian Avenue Yangtze River Tunnel, in which China Railway 14th Bureau participated in construction, into Nanjing's core urban areas such as Gulou District, Jianye District, and Yuhuatai District. This can significantly enhance the power mutual-support capacity across both banks of the Yangtze River, increasing power supply capacity by up to about 1 million kW, better promoting the construction of a new-type power system, and supporting Nanjing's high-quality development.