A 17.5-km-long tunnel of the China-Laos Railway was completed on Saturday in southwest China's Yunnan Province through four years of arduous efforts, laying a sound foundation for its opening to traffic in 2021 as scheduled.

The Anding Tunnel bordering Yuanjiang County and Mojiang County of Yunnan Province was jointly constructed by the China Railway 19th Bureau Group Co., Ltd. and the China Railway No.5 Engineering Group Co., Ltd.

During the process, constructors have endured many hazardous situations such as the harmful gas, water and mud inrushes, unfavorable geological conditions, among other dangerous scenarios.

"At that time, the water flow was very large, even as much as 50,000 cubic meters in volumes per day. It was difficult to drill the tunnel, with intensified efforts to cope with high water pressure. Generally, the water pressure could reach two MPa, with the lift of about 20 meters," said Wang Haifeng, the manager of the Yumo Railway Project of the China Railway 19th Bureau Group Co., Ltd.

"The bridge and tunnel ratio along the whole railway is relatively high, reaching a level of 87 percent. In addition, the proportion of tunnels is also large, accounting for 78 percent. There are 15 extra-long tunnels exceeding 10 kilometers along the railway," said Luo Shengli, director of the China-Laos Railway Tunnel Project of the China Railway Eryuan Engineering Group Co., Ltd.

The construction of the railway was divided into two sections, which were built simultaneously in China and Laos. Upon completion of the Anding Tunnel, some 84 out of the 93 tunnels within the Chinese territory have been drilled through and stand ready for operation.

The China-Laos Railway is an important infrastructure project linking the two countries. Upon opening to traffic, the travel will be shortened to only 8 hours from Kunming of Yunnan Province to Vientiane, the capital of Laos.