The friendship tunnel on the China-Laos railway line, the first cross-border tunnel, was dug through Sunday, laying a foundation for the operation of the railway in 2021.

The 9.59-kilometer tunnel is geographically special since the location where it was finally dug through is also where the borderline between the two countries converges.

At the construction site that is 7.17-kilometer away from the entrance of Mohan Port, workers were loading explosives, setting the detonating facilities to prepare for the final blast. At 08:00 on Sunday, with the completion of the blast, the tunnel was dug through. So far, around 97.5 percent of the tunnels on the Chinese section of the China-Laos Railway had been completed.

"We've finally completed it today. The tunnel was dug through. We are all very happy," said Pan Fuping, deputy production manager of project department of Yuxi-Mohan Railway under China Railway 2nd Bureau Group Co. Ltd.

The tunnel was excavated and built simultaneously in both China and Laos. It was rated first-level high risk project because complicated geological and geomorphological conditions pose many tough challenges to the construction. A large area of rock-salt geology in the construction site of Laos section had perplexed the constructors and engineers. After five expert consultations, under the technical support of the professional team and the scientific research group of universities, the construction plan was finally drawn up, which solved the world-level problem of high salt erosion and ensured the timely completion of the tunnel.

"The completion of the Youyi Tunnel marks another solid step forward in building the China-Laos railway -- a landmark project of China-Laos cooperation under the framework of the Belt and Road. At present, 80 tunnels of Yuxi-Mohan [Chinese section] of the China-Laos railway have been dug through, accounting for 97.5 percent of the construction. The construction of bridges and roads have largely been finished. The building of railway stations and track laying are carried out as planned," said Liu Juncheng, deputy commander of construction headquarters of Yunnan South Railway Construction Command under China Railway Kunming Bureau Group.

The 1,000 plus-kilometer China-Laos railway is the first international railway built mainly with Chinese investment, adopted Chinese technological standards, used Chinese equipment and directly connected with China's railway network. It will cut travel time from Kunming City to Jinghong City of Xishuangbanna Dai Autonomous Prefecture in southwest China's Yunnan Province to three hours, and ensure passengers reach Laos' capital city Vientiane within a day after it is completed and put into operation.