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)

LHASA, Dec. 2, 2019 (Xinhua) -- The rail-laying work of a 4,615-meter-long bridge crossing the Yarlung Zangbo River of Lhasa-Nyingchi railway in Sangri County of southwest China's Tibet was completed on Sunday.

The Lhasa-Nyingchi railway features complex geological conditions, with a total length of 435 km, 75 percent of which are bridges and tunnels. The construction work began in 2015 and is expected to be completed in 2021.

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)■