The Changla mountain tunnel [Photo/Agencies]

On Nov. 23 the Changla mountain tunnel officially opened to traffic. It is currently the world’s highest road tunnel at an average altitude of 4,499.98 meters, Xinhua reported.

The 2,400-meter-long tunnel is located in Zadoi County, Yushu Tibetan Autonomous Prefecture of Qinghai Province. Once the tunnel opens to traffic it will mark the connection of the 159.8-kilometer-long No. 309 provincial road from Duolamake to Zadoi.

As an important project for Yushu’s post-earthquake reconstruction and an important section in Qinghai Tibetan-inhabited area’s arterial highway network of secondary roads, the establishment of the Duolamuke-Zadoi road can improve Yushu’s ability to fight natural disasters and improve traffic-keeping. It can also promote regional resource development and tourism development.

The project leader from the Qinghai Traffic and Transportation Office said the project is located in an alpine region where the air is thin and the oxygen content of winter air is 40 percent of that on inland, making geological conditions of the tunnel complicated. Since Nov. 2011 the project has overcome the crossing of a fractured zone during construction, controlled the quality of the concrete under arctic temperatures and other technical problems.

"During the construction process, we have overcome problems such as water bursting and mudslides; the largest water inflow reached 18,000 cubic meters a day and we’ve overcome more than 60 large and small mudslides," said chief inspector of the Shanxi Jinda Traffic Construction Supervision Company Limited, Zhang Taijin, who has spent four years struggling hard at Changla mountain tunnel.