September 1

As the cutterhead of the 'Shanhe' shield machine slowly rotated

The Huanggang Road Yellow River Crossing Tunnel in Jinan

constructed by China Railway 14th Bureau Group

commenced tunneling

marking that the world's largest underwater shield tunnel

has begun its journey beneath the Yellow River

Zhou Changjin, General Manager of China Railway 14th Bureau Group (presiding over the overall work of the group), delivered a speech at the launching ceremony. He stated that since the project commenced, China Railway 14th Bureau Group has carefully planned and deployed, assembled elite forces, and integrated high-quality resources to advance the project with high positioning, high starting point, and high standards. With the strong support and cooperation of all parties, they have achieved this major milestone of shield launching. China Railway 14th Bureau Group will take this opportunity to continue to carry forward the spirit of the railway soldiers, move toward 'newness' and climb toward 'height', leverage the advantages of intelligent construction, continuously improve capabilities in smart construction sites, digital shield tunneling, monitoring and early warning, and build the Huanggang Road Yellow River Crossing Tunnel in Jinan into a quality project, safety project, green project, innovation project, and people's project that can stand the test, contributing central enterprise strength to the high-quality development of Shandong Province.

In recent years, Jinan has vigorously implemented the strategy of 'carrying the river northward and crossing it', with increasing density of transportation facilities crossing the Yellow River. The Huanggang Road Yellow River Crossing Tunnel in Jinan, where shield tunneling commenced this time, crosses the Yellow River and multiple roads along the route. It has a total length of 5,755 meters, with the shield section about 3,290 meters long. It will connect with the under-construction G309 interchange, opening up the major transportation artery on both sides of the Yellow River in Jinan.

To ensure the smooth construction of this world's largest underwater shield tunnel, the construction unit China Railway 14th Bureau Group customized the 'steel behemoth' — the 'Shanhe' shield machine. The equipment has a cutterhead diameter of 17.5 meters, equivalent to a six-story building, and is equipped with advanced technologies such as a pressurized composite cutterhead and telescopic main drive, as well as intelligent equipment systems including advanced geological forecasting and synchronous grouting detection. The overall assembly of the shield machine has reached the world's advanced level.

Compared with conventional shield machines, the system integration of 17-meter-class super-large-diameter shield machines is more complex, and the construction difficulty and risk coefficient increase geometrically. The 'Shanhe' shield machine has an excavation area of 240 square meters, and each ring of segments consists of 12 pieces, resulting in greater assembly risk, longer time, and more difficult precision control.

Thanks to the super-large excavation diameter, the tunnel adopts a single-tube double-deck structure, enabling two-way traffic with three lanes on each level. The application of super-large-diameter shield tunnels can effectively save urban underground space and is expected to save 15% of investment costs. Meanwhile, the single-deck clearance height of the tunnel is 4.2 meters, which can meet the requirements for buses, fire engines, and rescue vehicles, greatly improving traffic capacity.

The Yellow River stretches for thousands of miles and carries thousands of miles of sand. Beneath the Yellow River, the strata are rich in sand and gravel and silty clay. During the shield tunneling process, the lowest point is 63 meters below the water surface. The 5,200-ton 'steel behemoth' must traverse strata as sticky as 'rice cakes', and settlement control is key. Especially when crossing the Yellow River embankment, the maximum settlement must not exceed 1 centimeter. In addition, the Yellow River bed contains large amounts of calcareous concretions, like stones of various sizes embedded in a 'rice cake', posing huge challenges to tunnel construction.

To enable the shield machine to smoothly 'digest' this 'soft bone', the project team, relying on rich scientific research data from underwater tunnel construction, upgraded the shield machine's 'digestive system'. They adopted a customized cutterhead, equipped with tearing cutters suitable for the clay strata of the Yellow River basin and high-flow central scouring pumps, effectively addressing the problem of mud cake formation on the cutterhead and improving bottom slag discharge efficiency. At the same time, the synchronous dual-liquid grouting technology was adopted to achieve millimeter-level precision control of shield tunnel settlement.

In addition, to protect the ecological environment on both sides of the Yellow River, the project team adhered to the concept of 'green construction'. By increasing capital investment and adding filter press equipment, they carried out research on key technologies for harmless and cascade resource utilization of filter-pressed tail water, enabling the waste slurry treatment volume to meet daily advancement needs. This will also provide new solutions and technical approaches for the bottleneck problem of difficult mud tail water disposal in large Yellow River crossing tunnels in China.

The Jinan Huanggang Road Yellow River Crossing Tunnel Project is one of the major north-south passages across the Yellow River. Once completed, it will help interconnect the two sides of the Yellow River in Jinan, strongly accelerate the comprehensive development of the north bank of the Yellow River, promote Jinan's transition from the 'Daming Lake Era' to the 'Yellow River Era', and provide strong support for the ecological protection and high-quality development of the Yellow River basin.