Through water and toxic gases, China digs through new challenging tunnel

Chinese workers on Wednesday dug through a challenging tunnel after beating water and mud inrush, toxic gases and high temperature.

The Xinmin Tunnel in southwest China's Yunnan Province is part of a railway project linking the cities of Dali and Lincang. The tunnel construction lasted 1,520 days, according to the China Railway Kunming Group Co., Ltd.

The 8,287-meter tunnel was a challenging project due to its complex geological structures.

Water gushing and mud rushing in the tunnel's excavation surface were the most worrying situations for construction workers. The maximum water inflow was about 19,600 cubic meters per day.

The tunnel went through rock layers containing harmful gases, including carbon monoxide and sulfuretted hydrogen, and the builders had to endure temperatures up to 43 degrees Celsius.

Constructors applied high technology to predict the water-rich areas and reduce water pressure in advance, while high-power exhaust fans were installed to accelerate air circulation and lower the temperature inside the tunnel.

With a designed speed of 160 km per hour, the 202-km Dali-Lincang electrified railway will be the first railway linking Lincang, whose operation is expected to boost China's connectivity with neighboring countries.

Currently, the construction of 99.8 percent of tunnels and 99.6 percent of bridges on the line have been completed.