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The machine, which rolled off the production line in Chengdu, southwestern China's Sichuan Province, on Sept. 24, has an excavation diameter of 13.01 meters, stretches 220 meters and weighs 3,500 tons, making it the largest of its kind in the world, China Daily reported.
It was jointly developed by Chinese infrastructure company Shudao Investment Group and state-owned tunnel boring machine manufacturer China Railway Engineering Equipment Group.
Tunnel boring machines, or TBMs, use a rotating cutterhead to break through rock and soil while creating tunnels. Double-shield TBMs are designed to continue working across different geological conditions, including both stable and fractured rock.
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The Yuexi tunnel boring machine in Chengdu, China, Sept. 24, 2026. Photo courtesy of Shudao Group |
Yuexi can brace itself against stable rock as it bores and switch its support method when it encounters weaker formations, according to Chinese newspaper People's Daily.
Its cutterhead is equipped with 83 19-inch disc cutters, which press against and break up rock as the cutterhead rotates while hydraulic systems drive the machine forward.
During excavation, it can simultaneously bore through rock, install precast concrete tunnel segments, reinforce surrounding rock and remove excavated material.
It also carries drilling and geological detection systems that allow engineers to assess rock conditions ahead of the cutterhead before the machine reaches them.
An automatic laser guidance system can limit measurement errors to within three millimeters, allowing the machine to maintain millimeter-level navigation accuracy over excavation distances exceeding 10 km.
Yuexi will be used to excavate the Yuexi Tunnel on the Jinkouhe-Xichang Expressway in Sichuan's Liangshan Yi Autonomous Prefecture. The tunnel will stretch 18.4 km.
The TBM can advance more than 380 meters per month. The construction approach is expected to be three to five times as efficient as relying solely on conventional drilling and blasting.
The project marks the first use of a large-diameter double-shield TBM to excavate the main bore of an expressway tunnel in China. Such machines have more commonly been used for railway and subway tunnels.
