Jinan, a city of 9.4 million people and the capital of Shandong Province in East China, has made world headlines. Crews working there have completed the monumental task of building the world's largest-diameter underwater shield tunnel.
Using the largest available tunnel boring machine (TBM) on Earth, the China Railway 14th Bureau Group Co., Ltd. is still excavating the main section of the 3.6-mile (5,755 m) tunnel. The 2-mile (3,290-m) section of underwater shield segments, however, is complete.
This section is a colossal 55.8 ft (17 m) in diameter and consists of 500 pipe rings of underwater shielding, making it the largest-diameter tunnel of its kind anywhere in the world.
For comparison, the Channel Tunnel that connects the UK and France has three tunnels, two of which are the public rail tunnels with a diameter of about 25 ft (7.6 m) ... though it is significantly longer, at 31.4 miles (50.5 km).
The Jinan Huanggang tunnel will feature six lanes of travel in both directions in a double-decker configuration, with a 60 km/h (37 mph) speed limit. It will be a crucial north-south passage across China's second-longest river, the Yellow River, enhancing connectivity between Jinan's main urban area and what is described as "the starting area for the transformation of new and old kinetic energy."
Aside from setting a world record for the tunnel's sheer size, the 14th Bureau Group also set a world record for completion time for such a vast undertaking.
Crews began tunneling on September 1st, 2024, and while the entirety of the tunnel hasn't yet been completed, the underwater shielding portion has. It was accomplished in a mere 110 days. The Shanhe shield machine had a daily advancement rate of 52.5 to 59 ft (16 to 18 m), setting a new world record for 17-meter-class shield construction.
The boring machine in question is the Herrenknecht "Shanhe" Shield Machine, a mixshield tunnel boring machine boasting a 57.4-ft (17.5-m) excavation diameter – roughly 5 stories tall. The cutterhead driver has 7,510 hp (5,600 kW) and about 25,827,209 lb-ft (35,017 kNm) of torque. Yes, nearly 26 million lb-ft of electric motors and hydraulic power.
It's built to operate and withstand up to 7.5 bar of pressure (that's 7.5 times normal atmospheric pressure at sea level). The excavation chamber on the business end of the Shanhe can handle up to 15 bar using a specialized automatic air cushion to balance pressure, maintain stability, and prevent collapse or flooding.
The cutting wheel is equipped with a flushing system to help prevent clogging. It also has a telescopic camera system in the excavation chamber to monitor the cutting bits and tunnel face. This reduces the need for hyperbaric intervention by maintenance workers, which is time-consuming and dangerous.
If you want to get a Shanhe for yourself, it'll likely set you back at least US$80 million or so. This figure is based on the Santa Clara Valley Transportation Authority (VTA) in the US having shelled out a cool $76 million a 16.46-meter diameter Herrenknecht TBM.
The Jinan Huanggang Road Yellow River Crossing Tunnel is scheduled for completion sometime in late 2025.
Source: STDaily
