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.