China's largest shield tunneling machine rolls off the production line

China's largest shield tunneling machine rolled off the production line on Tuesday in Zhengzhou, central Henan Province.

The domestically developed "China Railway 1662" has a massive 16.68-meter excavation diameter and a body 125 meters long.

It weighs about 4,800 tonnes.

The extra-large boring machine cuts through rock or soil, removes debris, and installs concrete tunnel linings while protecting workers and equipment by holding back soil and water.

It uses an atmospheric-pressure cutterhead, which lets operators change cutters at normal pressure even when water pressure reaches 8 bar – roughly the pressure at a water depth of 80 meters.

The machine also features a circulation-based system to clear debris, combining direct discharge through a screw conveyor with crushing outside the working chamber.

The design means the slurry discharge pump can remove it without workers entering the chamber to repair the crusher.