On the 21st, the reporter learned from China Railway Construction Corporation that the world's longest heavy-haul railway under construction at one time has reached a key milestone. On that day, Asia's longest loess sandy tunnel, the 7,683-meter-long Wanrong Tunnel on the Mengxi-Huazhong Railway, was completed. The Mengxi-Huazhong Railway, with a total length of 1,837 kilometers, a transport capacity of 200 million tons, and an axle load of 30 tons, is China's fifth major coal transport corridor. The completion of the Wanrong Tunnel has laid the foundation for the entire line to be completed and opened to traffic in 2020.
　　Experts said that more than 97% of the Wanrong Tunnel consists of new loess and fine silty sand strata, and the geological difficulty is considered the greatest in the world. “Digging a tunnel is as difficult as hollowing out a hole in a sand dune; often, when one cubic meter is excavated, a pile of sand flows out.” Zhang Hua, project manager of the China Railway 12th Bureau Group, which is undertaking the construction task, said that in order to turn the loose sand layer into a hard shell, the project department, together with Southwest Jiaotong University and other institutions, overcame the world-class technical challenge of “excavation in fine silty sand strata” and also set a tunneling record for tunnels of the same type in the world, doubling construction efficiency.
　　The construction of the Wanrong Tunnel achieved a total of 14 scientific and technological innovation results, and it is also the first tunnel in China to use three technologies in combination for construction: a 46-meter invert trestle, one-time ring closure of initial support, and advance reinforcement by horizontal jet grouting rigs.