A domestically built super-large-diameter slurry shield machine rolls off the production line in Hangzhou, East China's Zhejiang Province, on October 22, 2026. Photo: anhuinews.com

A domestically built super-large-diameter slurry shield machine rolled off the production line in Hangzhou, East China's Zhejiang Province, on Thursday and will soon be deployed to a construction project in Hefei, East China's Anhui Province. 

With an excavation diameter of 16.68 meters and a total length of about 125 meters, the machine marks a key technological breakthrough in China's super-large-diameter slurry shield equipment, according to anhuinews.com, a provincial state-owned news outlet

The shield machine, China Railway 1659, has an overall length of 125 meters — equivalent to the height of a five-and-a-half-story building. With a maximum thrust of 28,149 tons and a total weight of about 4,800 tons, it ranks among the top-tier machines of its class currently available in China.

The machine was jointly developed by China Railway No.4 Engineering Group, China Railway Tunnel Group and China Railway Engineering Equipment Group. It will be used for a major transportation project in Hefei. This marks a key technological breakthrough for China's super-large-diameter slurry shield equipment in handling complex conditions such as hard rock, fault fracture zones, underwater sections, small-radius curves, and steep slopes, according to anhuinews.com.

The machine incorporates customized and innovative technologies. It is equipped with a circulating slurry discharge system, adopting the industry-leading "screw conveyor direct discharge + out-of-chamber crushing" slurry treatment mode that ensures efficient muck discharge by the slurry pump, and avoids the operational risk of entering the chamber to repair the crusher, building a solid safety defense line for underwater tunnel construction.

It is also equipped with six intelligent systems —sensing, tunneling, segment erection, environmental control, management, and slurry treatment — to ensure safe underwater excavation.

China has been developing large shield machines for complex underwater and urban tunnel projects.

In September, another super-large shield tunneling machine named China Railway 1662 rolled off the production line in Zhengzhou, Central China's Henan Province, which will also be used in the Hefei construction project. 

The machine, with an excavation diameter of 16.68 meters, uses an atmospheric-pressure cutterhead, which lets operators change cutters at normal pressure even when the water pressure reaches 8 bar - roughly the pressure at a water depth of 80 meters.

The Hefei project, the West Extension Project of the North Second Ring Road, is a vital east-west artery of the city's expressway network. Upon completion, the project will shore up weak links in the road network of the main urban area, strongly underpinning Hefei's strategy of boosting urban development through science and innovation as well as the construction of a modern, international and innovative city, said the report.

Global Times