HUANJIANG — The Jiuwandashan No 4 tunnel in Huanjiang Maonan autonomous county, South China's Guangxi Zhuang autonomous region, was drilled through on Aug 17, marking the completion of all 108 tunnels of Guiyang-Nanning high-speed railway line.

The 15,485-meter tunnel is the longest first-class high-risk tunnel in the Guangxi section of the high-speed railway.

The Guiyang-Nanning high-speed railway, with a maximum speed of 350 km per hour, is expected to go into service in 2023.