Surveyors from the Survey and Mapping Institute under China Railway Eryuan Engineering Group Co., Ltd. conduct surveys for the Sichuan-Tibet Railway on Zheduoshan Mountain in Kangding, southwest China’s Sichuan province, Feb. 18, 2020. Construction of the Sichuan-Tibet Railway, the second railway to go into Tibet, has been making steady progress. Recently, 47 tunnels along the Lhasa-Nyingchi section of the railway have been bored, laying a solid foundation for the operation of the section. (Photo/Zhang Wen)

Workers celebrate the holing through of the Milin tunnel, a key project in the Lhasa-Nyingchi section of the Sichuan-Tibet Railway in southwest China's Tibet autonomous region, April 7, 2020. Construction of the Sichuan-Tibet Railway, the second railway to go into Tibet, has been making steady progress. Recently, 47 tunnels along the Lhasa-Nyingchi section of the railway have been bored, laying a solid foundation for the operation of the section. (Photo/Jue Guo)

Workers from China Railway Electrification Engineering Group install ratchet wheel frames between Nyingchi and Kangar on the Lhasa-Nyingchi section of the Sichuan-Tibet Railway in southwest China's Tibet autonomous region, April 2, 2020. Construction of the Sichuan-Tibet Railway, the second railway to go into Tibet, has been making steady progress. Recently, 47 tunnels along the Lhasa-Nyingchi section of the railway have been bored, laying a solid foundation for the operation of the section. (Photo/Xu Yuyao)

This photo taken on April 23, 2020 shows the first long rail transported to the Xierong paving base since construction of the Lhasa-Nyingchi section of the Sichuan-Tibet Railway was resumed this year. Construction of the Sichuan-Tibet Railway, the second railway to go into Tibet, has been making steady progress. Recently, 47 tunnels along the Lhasa-Nyingchi section of the railway have been bored, laying a solid foundation for the operation of the section. (Photo/Yuan Quan)

A worker from China Railway 11 Bureau Group measures the temperature of concrete during the concreting process at a beam fabrication construction site on the Lhasa-Nyingchi section of the Sichuan-Tibet Railway at the beam fabrication yard in Nang county, southwest China's Tibet autonomous region, May 9, 2020. Construction of the Sichuan-Tibet Railway, the second railway to go into Tibet, has been making steady progress. Recently, 47 tunnels along the Lhasa-Nyingchi section of the railway have been bored, laying a solid foundation for the operation of the section. (Photo/Yuan Quan)

This photo shows rail being welded at the Lhasa-Nyingchi section of the Sichuan-Tibet Railway in southwest China's Tibet autonomous region. The seamless long rail welding of the section was completed smoothly on April 16, 2020. Construction of the Sichuan-Tibet Railway, the second railway to go into Tibet, has been making steady progress. Recently, 47 tunnels along the Lhasa-Nyingchi section of the railway have been bored, laying a solid foundation for the operation of the section. (Photo/Yuan Quan)