On August 17, the Jinan Huanggang Road Yellow River Tunnel, a project built by CRCC, was completed. This marks a significant milestone for China's underwater tunnel construction, as it is the  world's largest-diameter underwater shield tunnel.

Stretching 5.75 kilometers with a design speed of 60 km/h, the tunnel is the first of its kind to cross the Yellow River using a single-tube, double-deck shield design. This innovative structure features a total of six lanes on two levels, which not only maximizes underground space but also cuts investment costs by approximately 15%. With a clear height of 4.2 meters, it can accommodate buses, fire engines, and rescue vehicles, substantially boosting the city’s traffic capacity.

To tackle this ambitious project, the team engineered "Shanhe", the world's largest-diameter slurry shield machine currently in use. This highly advanced machine is equipped with a special compound cutterhead, a telescopic main drive, and an intelligent system for real-time sensing, warnings, and smart decision-making. The team's ingenuity was especially evident in solving the challenge of severe cutter wear. They developed diamond tools and a double-pipeline hydraulic rock-picking device, which for the first time allowed for continuous excavation of 3.3 kilometers beneath the Yellow River without the need for a single cutter change.

The project also achieved major breakthroughs in environmental protection and safety. A new, more efficient mud-treatment process was developed, boosting efficiency by 50% and enabling a zero-discharge water recycling system. To prevent the flotation of the extra-large tunnel segments, a fourth-generation synchronous dual-fluid grouting technology was employed, limiting segment uplift to a mere 5 millimeters. The team also installed high-precision monitoring equipment along the route for round-the-clock surveillance, ensuring the shield’s safe and steady progress. These efforts helped the team overcome 28 technical challenges and set two world records for a 17-meter-class shield machine: a daily advance of 18 meters and a monthly advance of 426 meters. The project also resulted in a comprehensive construction technology system, over 30 academic papers, and 22 patent applications.

Once operational, the tunnel is expected to greatly enhance economic cooperation between the north and south banks of the Yellow River. This will not only strengthen the provincial capital's central role but also play a critical part in implementing China's national Yellow River strategy and accelerating the development of the region's new economic hub.