World's largest double-shield TBM rolls off production line in Chengdu

A double-shield tunnel boring machine (TBM) with a diameter of 13.01 meters rolled off the production line on Thursday in Xinjin district, Chengdu, Sichuan province, becoming the largest of its kind in the world.

Named Yuexi, the machine is jointly developed by Shudao Investment Group and China Railway Engineering Equipment Group. It is 220 meters long, roughly the length of a standard high-speed train, and weighs 3,500 metric tons, making it about as heavy as 800 adult Asian elephants.

The TBM consists of 37 systems and is three to five times more efficient than conventional drill-and-blast methods. It can also keep workers away from high-risk areas and minimize the impact of construction on the surrounding environment, the developers said.

The machine will soon be used to build the Yuexi Tunnel on the Jinkouhe-Xichang Expressway in Sichuan. The tunnel, which adopts a separated twin-tube design, stretches about 18.4 kilometers, with a maximum burial depth of 1,011 meters.

Upon completion, the expressway will end the history of having no expressway access in the three counties of Ganluo, Yuexi, and Xide in Liangshan Yi autonomous prefecture.