LHASA — The track-laying work was completed on Dec 31 for a railway linking the cities of Lhasa and Nyingchi in Southwest China's Tibet autonomous region.

With a designed speed of 160 km per hour, the 435-km rail line passes through 47 tunnels and 120 bridges, according to its constructor Tibet Railway Construction Co Ltd, a subsidiary of China State Railway Group.

Construction started in 2014 on the railway connecting Lhasa, the regional capital, and Nyingchi in eastern Tibet. It is the first electrified railroad in Tibet and is slated to begin operations in June 2021.

So far, a total of 31.2 billion yuan (about $4.8 billion) has been invested in the project, according to official data.

With more than 90 percent of the railway built in areas more than 3,000 meters above sea level, the high altitude and complex geological conditions have posed great challenges to the project.

Zhu Jintang, deputy general manager of Tibet Railway Construction Co Ltd, said the constructors have stepped up scientific research to tackle key problems in tunnel construction such as high ground stress and extreme temperatures.

Zhu said they have obtained more than 30 patents during the project, which will provide valuable experience for the ongoing construction of the Ya'an-Nyingchi section of the Sichuan-Tibet Railway.

The completion of the track-laying on the Lhasa-Nyingchi railway marks important progress in the building of the Sichuan-Tibet Railway that will connect Lhasa and Chengdu, capital of the neighboring province of Sichuan.