Photo taken on Dec. 1, 2019 shows the construction site of a bridge crossing the Yarlung Zangbo River of Lhasa-Nyingchi railway in Sangri County of Shannan, southwest China`s Tibet Autonomous Region. (Xinhua/Chogo)

Workers of China Railway 11 Bureau Group Co., Ltd. lay steel rail for a bridge crossing the Yarlung Zangbo River of Lhasa-Nyingchi railway in Sangri County of Shannan, southwest China`s Tibet Autonomous Region, Dec. 1, 2019. (Xinhua/Chogo)

Workers of China Railway 11 Bureau Group Co., Ltd. lay steel rail for a bridge crossing the Yarlung Zangbo River of Lhasa-Nyingchi railway in Sangri County of Shannan, southwest China`s Tibet Autonomous Region, Dec. 1, 2019. (Xinhua/Chogo)

Workers of China Railway 11 Bureau Group Co., Ltd. lay steel rail for a bridge crossing the Yarlung Zangbo River of Lhasa-Nyingchi railway in Sangri County of Shannan, southwest China`s Tibet Autonomous Region, Dec. 1, 2019. (Xinhua/Chogo)

Photo taken on Dec. 1, 2019 shows the construction site of a bridge crossing the Yarlung Zangbo River of Lhasa-Nyingchi railway in Sangri County of Shannan, southwest China`s Tibet Autonomous Region. (Xinhua/Chogo)

Photo taken on Dec. 1, 2019 shows a bridge above the Yarlung Zangbo River of Lhasa-Nyingchi railway in Sangri County of Shannan, southwest China`s Tibet Autonomous Region. (Xinhua/Chogo)