Jinan, the capital of Shandong province with a population of 9.4 million in eastern China, has completed construction of the world’s largest diameter underwater trestle tunnel.
Using the largest tunnel boring machine (TBM) available, the China Railway 14th Bureau Group company is digging the main section of the 5,755 m long tunnel. However, the 3,290 m long underwater platform section has been completed, New Atlas reported on December 20. This section has a diameter of 17 m and includes 500 rings of pipe forming an underwater truss, making it the largest diameter tunnel of its kind in the world. Compared to it, the Channel Tunnel connecting England and France has 3 tunnels, two of which are railway tunnels with a diameter of 7.6 m although much longer (50.5 km).
Jinan Huanggang Tunnel will consist of 6 lanes in both directions with a double deck configuration, with a speed limit of 60 km/h. This will be an important north-south corridor across China’s second largest river, the Yellow River, strengthening connectivity between Jinan’s main urban area. In addition to the world record for tunnel size, Bureau 14 Group also set a record for construction completion time.
The crew started digging the tunnel on September 1, 2024. Although the entire tunnel is not yet complete, they completed the construction of the underwater truss section in 110 days. The Shanhe shield tunneling machine has a daily travel speed of 16 to 18 m. With a diameter of 17.5 m, the machine is as tall as 5 floors. The cutting head propulsion motor has a capacity of 5,600 kW and a torque of 35,017 35,017 kNm.
The machine is manufactured to operate and withstand pressure 7.5 times the normal pressure level at sea level (7.5 bar). Shanhe’s end excavation chamber can withstand pressure of up to 15 bars thanks to the use of specialized automatic air cushions to equalize pressure, maintain stability, and prevent collapse or flooding.
The cutting wheel is equipped with a drain system that helps prevent clogging. The machine also has a far-view camera system in the excavation chamber to monitor the cutting head and tunnel surface. This reduces the need for intervention by maintenance workers, which is time-consuming and dangerous.
The Jinan Yellow River Crossing Tunnel is expected to be completed by the end of 2025.