The Friendship Tunnel, the only cross-border tunnel of the China-Laos Railway, was dug through on Sept 13, laying a solid foundation for the full operation of the entire line.
Located at the border of the two countries, the tunnel has 7.17 kilometers in China and 2.42 kilometers in Laos and a designed speed of 160 kilometers per hour.
Designed by China Railway Eryuan Engineering Group Co., Ltd and contracted by China Railway No. 2 Engineering Group Co., Ltd., the tunnel was named after the deep friendship between the people of the two countries.
The tunnel was dug through complicated geological stratum with unproved faults and surrounding rock made up of mudstone, sandstone, rock salt and gypsum. The rock mass is fragile with poor auto-stability and turns soft in water.
As the weak surrounding rock can easily cause collapse and deformation, builders used special engineering skills to shorten exposure duration and ensured in-time sealing of the surrounding rock, which overcame deformation and guaranteed construction progress.
In addition to other geological challenges, the tunnel was built through rock salt that was a strong corrosion threat to the tunnel.
To guarantee construction quality, C50 and C45 concrete with high duty and strong corrosion resistance was used. What's more, the reinforcing steel bars were made of epoxy resin, which is like adding a protective covering to the bars to protect them from the salty water.
A 65-meter trestle and whole-sealing anti-floating templates were also used during construction, which guaranteed quality, safety and progress despite seepage of the underground water and the rock salt water.
So far, 80 tunnels have been completed on the Yuxi-Mohan section in China and 97.5 percent of the last 13 tunnels have been finished. Construction of roadbed and bridges is primarily completed and other construction including track-laying and stations is progressing smoothly.
The China-Laos Railway was built to Chinese standards with China-made equipment and was mainly invested by a Chinese enterprise. It was the first of its kind to link Chinese railway with a foreign country.
Stretching more than 1,000 kilometers, the railway is a result of China's Belt and Road Initiative and Laos' strategy to evolve into a land-linked country from a land-locked country.
Once operable, it will take passengers only three hours to travel between Kunming and Jinghong in Yunnan and about 12 hours to go from Kunming to Vientiane, capital of Laos.
(Executive editor: Wang Ruoting)
