On March 26, construction of the Nanjing Shangyuanmen river-crossing passage is advancing at full speed. The south-bank working shaft and the first-phase retaining structures, main structures, and pile foundations of the cut-and-cover tunnel have been completed, with excavation of the foundation pit scheduled to begin early next month. As the core project linking Nanjing North Station, Nanjing Station, and Nanjing South Station, this passage is Nanjing's first high-speed railway river-crossing tunnel. Featuring the technical characteristics of "longest length, highest water pressure, and greatest burial depth," it sets multiple national records for high-speed railway river-crossing tunnel construction and will serve as the key project opening up Nanjing's north-south cross-river high-speed rail network.

Nanjing's First High-Speed Railway River-Crossing Tunnel to Begin Foundation Pit Excavation Soon

The Nanjing Shangyuanmen river-crossing passage starts from Nanjing North Station in Jiangbei New Area in the north and connects to Nanjing Station in the main city in the south, with a main line length of approximately 20.4 kilometers. It is the core project for opening up Nanjing's north-south high-speed rail network and achieving cross-river connectivity. Among its sections, the pre-station Section 4, constructed by China Railway Tunnel Group, has a main line length of approximately 8 kilometers. The shield-driven section, as the most critical controlling project of the entire line, fully demonstrates the extremely high difficulty of construction.

The project adopts a single-tube, double-track high-speed railway tunnel design and requires precise shield tunneling beneath the Yangtze River bed, with a single-head tunneling distance of 6,803 meters in the shield section. The geological conditions along the construction route are complex, requiring sequential crossing of various strata including mudstone, sandstone, fault gouge with breccia, and karst areas, posing significant challenges to the tunneling work.

According to Liu Li, Mechanical Chief Engineer of the China Railway Tunnel Group project, the shield section bears a maximum water pressure of 1.07 MPa, equivalent to approximately 11 kilograms of pressure per square centimeter. The lowest point of the tunnel has an elevation difference of 107 meters from the Yangtze River water surface, with a maximum burial depth of 91 meters, ranking among the top in domestic high-speed railway river-crossing shield tunnels.

Nanjing's First High-Speed Railway River-Crossing Tunnel to Begin Foundation Pit Excavation Soon

At the same time, the route must sequentially pass beneath residential communities, metro lines, and ecological control zones, imposing extremely high requirements on stratum settlement control and surrounding environmental protection during construction. "Every step of construction must be precisely controlled—we must ensure the safety of the tunnel structure while avoiding impacts on residents' lives and metro operations along the route. This is a real test of our construction techniques and management capabilities," said Liu Li.

Currently, the retaining structures, main structures, and pile foundations of the south-bank working shaft and the first phase of the cut-and-cover tunnel have all been completed, marking phased achievements in the project. The construction focus has now shifted to crown beam and support construction. According to plan, this section is expected to officially begin foundation pit excavation early next month, laying a solid foundation for subsequent shield tunneling.

As a key project in the National Development and Reform Commission's "Yangtze River Trunk River-Crossing Passage Layout Plan," the Nanjing Shangyuanmen river-crossing passage is not only the "key horizontal link" connecting Nanjing North Station and Nanjing Station, but will also undertake the river-crossing responsibilities of the Nanjing-Huai'an Intercity Railway and the Shanghai-Chongqing-Chengdu High-Speed Railway. It will also connect the three major hubs of Nanjing North Station, Nanjing Station, and Nanjing South Station "on a single line," forming a new pattern of "three-station linkage."

Source:Yangtse Evening Post Online