XI. China's largest water tunnel that goes through giant rivers – the Yellow River Crossing Tunnel of the central route
To adjust to the wandering and silt-foundation features of the Yellow River, the Yellow River Crossing Tunnel Project is consisted of two tunnels which are both 4,250 meters long and seven meters in inner diameter. Both tunnels have a two-layered structure, with the inner layer and the outer layer separated by a permeable barrier so that each layer can endure water pressure both in and out of the tunnel. This kind of structure is a first in the world. The Yellow River Crossing Tunnel Project has been completed, setting a new record for China's long-distance underwater tunnel construction in soft soil.