Chunnel
...boring machines (TBMs), but the French were much more advanced in other machinery. The French used machine-built cages to reinforce the tunnel, where as the British used handmade steel liners and concrete segments. The French used cranes to lift tunnel segments into place, and the British fitted the segments by hand. The French side used 252,000 segments and the British used 422,755 segments. The massive TBMs weighed nearly 1300 tons and were made in the United States. The tip of the TBM was around 10m in diameter, and the TBMs were nearly 200 yards long (length of 2 football fields). Boring capabilities of the TBMs was 250 ft/day. The cutter heads were made of tungsten teeth. Laser probing was used so that the TBMs would remain on course at time when they met up. When the tunnels met up in the middle, the TBMs were buried in the walls of the tunnel. 11 TBMs were used on the project costing $90 million dollars. The debris is carried by a conveyor belt through the back of the TBM and then it is removed from the tunnel. The rubble increased the size of Britain’s coast by 90 acres. The soil conditions underneath the channel are almost perfect for tunneling. Most of the material is made up of chalk marl. Chalk marl is a sedimentary rock that is soft but stable, and impervious to water which makes it almost the perfect tunneling material. There is nearly 60 meters of rock above the tunnel. The Western Channel is flat and uniform, and made up of mostly limestone. The Central and Eastern Channels are made up of mostly clay and limestone. Although the rock was ideal for tunneling, several geological problems were encountered during the tunnel construction. On several occasions the TBMs hit chalk which was penetrable by water and the tunnel became flooded. This severely delayed progress in the tunnel because all water had to be removed before tunneling could continue. Some of the material would crumble due to the weight of all the layers. This would occur before crews could reinforce the concrete tunnel segments. The conveyor belts on the TBMs jammed regularly. All of these factors forced the tu...