17.6-km-long Xiuling Tunnel drilled through in Yunnan, setting record for longest single-track tunnel in Asia

The 17.6-kilometer-long Xiuling Tunnel, an important part of the China-Myanmar International Railway Corridor, was drilled through in southwest China's Yunnan Province on Wednesday, after 13 years of hard work. Its length of 9,677 meters has set a record for the longest single-track mountain tunnel in Asia, according to data from China State Railway Group Co., Ltd.

With a total length of 17.62 kilometers, Xiuling Tunnel, parallel to the main tunnel, is a key project of the Dali–Ruili Railway, located in Yangbi County of Dali Bai Autonomous Prefecture.

Due to the complex geological environment of soft rock, workers could not construct the tunnel from various work surfaces, which prolonged the construction period from the original five and a half years to 13 years.

"At present, the construction methods of access adit, inclined shafts, and vertical shafts are mostly employed in digging extra long tunnels in China now, increasing the excavation work surface and realizing short excavation. Limited by geology and terrain, Xiuling Tunnel could only be excavated for a long distance at both ends of the entrance and exit. As a result, it was very difficult for workers to speed up the progress of the tunnel construction. The slow advancement of the tunnel construction has become a big obstacle affecting the completion of the entire Darui Railway," said Qiao Zhiqiang, director of the Xiuling Tunnel Exit Project of China Railway No. 8 Engineering Group Co., Ltd.

Engineers on the project took targeted measures and adopted innovative construction technologies to solve various complex problems. For example, they adopted a boom-type road header to excavate the tunnel, plus the traditional drilling-blasting method allowed them to properly deal with different geological conditions.

"There are 21 tunnels in the Dali-Baoshan section of the Dali Railway, 18 of which have been drilled through. The opening of Xiuling Parallel Tunnel will provide favorable conditions for the subsequent construction of other tunnels," said Zhang Wei, deputy director of the Command Department of the Darui Railway Construction Project of the China Railway Kunming Group Co.,Ltd.

With a total length of 330 kilometers, Darui Railway will connect the last section of the China-Myanmar International Railway in China after completion, improving the transportation pattern in western Yunnan and becoming an important trunk line of the China-Myanmar Railway.