China is building the Jintang railway tunnel under the sea between Ningbo and Zhoushan. A machine called Yongzhou is digging part of it. The machine is 135 metres long. Engineers control it from a centre about two miles away, above ground.
Cameras and tools send information about the machine and warn engineers about problems. Workers also stay inside to watch the work. Yongzhou has dug more than 4,000 metres from the Ningbo side. It has finished about 83 per cent of its planned digging.
The machine is getting close to a point 93 metres below the sea floor. It faces hard rock and soft ground, and workers have already changed about 4,000 cutting parts. For repairs, workers enter an area with high air pressure. They live in a special room with high air pressure between work periods.
Yongzhou will meet another digging machine called Dinghai inside the tunnel. Workers will then take both machines apart there. The whole tunnel is 16.18 kilometres long, and the railway is expected to open in 2028. The fast train journey between Ningbo and Zhoushan will take 26 minutes.
