Construction on the 47 tunnels on a 435-km railway linking Lhasa and Nyingchi in southwest China's Tibet Autonomous Region was completed Tuesday.

The completion of the two tunnels has increased the total tunnel length to 216.5 km, almost half of the railway length.

Mainling Tunnel, located in the city of Nyingchi, is 11,560 meters long with an average elevation of 3,100 meters above sea level and a maximum burial depth of about 1,200 meters.One of the most difficult tunnels ever built.

The 8.7-km Zagar Tunnel in the city of Shannan traverses seven faults of complex geological structures.

http://www.xinhuanet.com/english/2020-04/07/c_138954375.htm