New Guanjiao Tunnel [1](Chinese: 新关角隧道; pinyin: Xīn Guānjiǎo Suìdào) is a tunnel on the 2nd line of Qinghai–Tibet Railway in Guanjiao Mountain, Qinghai province. It is dual-bored, double-track rail tunnel. The total length of the tunnel is 32.645 km (20.285 mi), which made it at the time of completion the longest railway tunnel in China and fourth-longest in the world.
China Railway First Survey and Design Institute is responsible for the design. The New Guanjiao Tunnel was designed for two parallel single-track tunnels with speeds of up to 160 kilometres per hour (99 mph). The total construction duration was projected to be 5 years. The tunnel was bored in difficult geological conditions and high altitude, exceeding 3,300 metres (10,800 ft) above sea level. The construction started in 2007 and was completed in April 2014.[2] The tunnel was opened on 28 December 2014.[3]
The tunnel's northeastern portal (37°11′00″N 99°10′40″E / 37.1834°N 99.1778°E / 37.1834; 99.1778) is in Tianjun County, the southwestern portal (37°00′34″N 98°52′50″E / 37.0094°N 98.8805°E / 37.0094; 98.8805) is in Ulan County.
