Enormous utility galleries, a powerful shield tunneling machine, a white-toned construction site…… If I hadn't experienced it myself, I truly wouldn't have believed that this scene, so full of technological sophistication, was the construction site of the Yellow River crossing tunnel.

The Jinan Yellow River Tunnel is advancing at a rate of 8 rings (16 meters) per day. According to project secretary Li Gaochun, the project is currently the largest-diameter road-rail combined tunnel under construction in China. As the first super-large-diameter shield tunnel in China to cross a perched river above ground, it is hailed as the “First Tunnel of the Ten-Thousand-Li Yellow River.” The Jinan Yellow River Tunnel has a total length of 4,760 meters and is designed as a double-tube, double-level crossing beneath the Yellow River, with a segment outer diameter of 15.2 meters and an inner diameter of 13.9 meters. The upper level carries a six-lane dual-carriageway road, while the lower level reserves space for rail transit, smoke ducts, longitudinal escape passages, and utility galleries.

To enhance comprehensive urban functions, accelerate the conversion of old and new growth drivers, and speed its transition from the “Daming Lake era” to the “Yellow River era,” Jinan held the foundation-laying ceremony for the Jinan Yellow River Tunnel project on November 28, 2017, opening a new era in which the Ten-Thousand-Li Yellow River natural barrier is crossed not only above the water but also beneath it. The Jinan Yellow River Tunnel project adopts the engineering, procurement, and construction (EPC) general contracting model, with a planned total construction period of 45 months. The client is Jinan Urban Construction Group, and the China Railway 14th Bureau Group leads and organizes construction.

Li Gaochun explained that the project is located on a first-level terrace of the Yellow River, where groundwater is abundant and the water table is high. The foundation pit has a maximum excavation depth of 35 meters and a width of 50 meters, making it the deepest and widest foundation pit ever excavated in the Jinan area. With no analogous engineering experience to draw on, risks include groundwater inflow into the pit and support instability. The diaphragm walls reach a maximum depth of 60 meters, entailing high hoisting risks and great construction difficulty.

It is understood that this is the first time a super-large-diameter shield tunnel has crossed a perched river above ground, and construction risks are high. The project uses two of the world's most advanced German Herrenknecht slurry shield machines for the shield-driven excavation. Based on the surveyed geological conditions, the shield machines were “tailor-made” in terms of selection.

The shield-driven section has a burial depth of 26.3 to 54.6 meters, and the strata it passes through are mainly silty clay. When the shield machine tunnels through calcareous concretion strata, it is prone to tool wear and cutter-tooth breakage. These are key focuses of shield construction and also difficulties in schedule control.

According to the plan, once the tunnel is completed in 2021, it will take only 4 minutes to cross the Yellow River from the urban area. The north bank of the Yellow River will no longer be a suburb of Jinan but will be integrated with the urban area as a single district, truly realizing Jinan's dream of cross-river development.