Tunnel boring machines for the Yangtze River 

In 2009 the inhabitants of the Chinese metropolis Nanjing will be able to cross the Yangtze River through a tunnel excavated by tunnelling machines with an external diameter of 14.5 metres. This is close to the world record size.

COWI is involved in preparing the specifications for the two boring machines, which must be capable of operating in difficult soil conditions.

Drilling in soft strata

The two boring machines to be used on the project not only have to be big in size, but also able to drill through the soft river deposits of clay, silt and sand located just 10 metres beneath the bed of the Yangtze River.

The tunnel boring machines will be slurry machines, particularly well-suited to drill in soft materials such as sand and clay, which are characteristic of the river deposits of Yangtze.

"This kind of boring machine conveys away the soil extracted and supports the tunnel front by means of a stabilising mixture of excavated material and bentonite," explains Søren Degn Eskesen, the Project Manager from COWI.

Growth potential in China

China is a large market, and the need for tunnels is expanding vigorously, partly due to large investments in the country’s infrastructure.

Apart from the tunnel project at Nanjing, COWI is involved in another Chinese tunnel project under the Yangtze River near the island of Chongming, just off Shanghai. This tunnel is part of another project that involves traversing the Yangtze River with a six-lane motorway tunnel. This will also be constructed using slurry boring machines.

Published: 12.08.05
By: Line Steenberg, jaje@cowi.dk