The Worlds Biggest Machines

Introduction | Biggest Engine | Biggest Aeroplane | Biggest Cargo Ship |
| Biggest Truck | Biggest Mobile Crane |
| Tunnel Boring Machine | Rolling Mill | Part Eight |
| Part Nine | Part Ten |

Early rail tunnels, built in the mid 1800s, were dug by mainly by hand with pick and shovel after being 'blown' by dynamite. Modern methods of excavation and tunnel digging have advanced considerably since that time resulting in faster construction times and less lives lost. While still a dangerous process the number of tunnelling accidents that occur each year in the developed world are few, compared to the high mortality rate in the early days.

One of the greatest advances in tunnel construction has been the introduction of automated tunnel boring machines (TBM's) that can munch their way through rock and soil 24 hours a day. These massive machines now feature in projects across the globe. The biggest was built in Germany.

The S-317 Mixshield

TBM Manufacturer Herrenknecht based in Schwanau, South Germany, designed and built the S-317. The cutting head is an enormous 15.43 metres in diameter and will operate at the Changjiang Under River Tunnel Project in Shanghai, Japan. Two of the units have been produced, named 317 and 318, and will each construct one of two three-lane road tunnels both measuring 7.2km in length.

The machines will be required to work below the Yangtze River at depths of up to 65 meters until the project is completed in 2010 ahead of the Shanghai World Expo.

TBM's come in all shapes and sizes. The major differences come at the cutting face or 'shield' where they are individually designed to remove different substrata. Most TBM's are happiest crunching away at rock or solids, but deep beneath river beds the going gets damp and Mixshield or 'slurry tunnelling' technology is employed.