The Changla Mountain Tunnel opens on Jun. 25. [Photo/Agencies]

The world’s highest altitude highway tunnel - the Changla Mountain Tunnel – saw an opening to traffic on Jun. 25, 2015, Xinhua reported.

The Changla Mountain Tunnel has a total length of 2,400 meters, and is located in Yushu Tibetan Autonomous Prefecture, Qinghai Province, at an altitude of about 4,500 meters.

The tunnel was a key engineering project on the section between Dorak Make and Dzatod counties of the Qinghai Provincial Highway 309. It is also an important part of Yushu’s earthquake recovery and reconstruction, known as the modern “Tang-Tubo Ancient Road”.

According to GaoYouguang, project manager of the China Railway 14th Bureau Group, the project is located in an alpine region where the air is thin and in winter the oxygen content is only 40 percent of that in the inland. Additionally, the region has snow in all four seasons.

The tunnel was built in complex geological conditions including water flows, fault zones, and frequently cracking rocks, all of which made construction very difficult. There was a shortage of suitable supplies at the project location, so materials had to be transported from up to 1,000 kilometres away, amidst logistical difficulties.

Since construction began in November 2011, the builders have overcome the problems of high altitude permafrost and the local fault zones to build the tunnel, even overcoming a number of technical problems such as concrete quality control in the extremely cold temperatures.

Throughout the construction project, workers have accumulated technical knowledge and management experience from working in the high altitude and extreme cold. The construction of the new highway will help improve infrastructure in the quake-stricken area and the capability for disaster relief support, which will be of importance to the development of the natural resources and tourism in Yushu.

The Changla Mountain Tunnel opens on Jun. 25. [Photo/Agencies]

The Changla Mountain Tunnel opens on Jun. 25. [Photo/Agencies]