Thousands of people take the Tube from the N side of London to the south , or pop across the English Channel via the Channel Tunnel every day , but they ’re only able to do so thanks to one pretty important feature – underwater tunnel . But how is such an impressive exploit of technology build ?
The tunneling shield
submerged tunnels had people stumped until Gallic - British engineer Marc Isambard Brunel ask divine guidance from nature back in 1818 . After watching how a teredinid ’s case plates allowed it to bore through Sir Henry Joseph Wood , Brunel took that principle and scale it up into thetunneling shield .
In this slip , it was a jumbo , rectangular cast iron casing withshutter openingson its wall , which were opened one at a time so that miners could labor forth the piano earth alfresco . The shield was then agitate frontwards using fuck jacks and the summons repeated , with the protective “ carapace ” of the tunnel built out of bricks in the freshly carve region behind .
This lead to thefirst - ever submerged tunnelbeing built under the River Thames in London , completed in 1842 . Later tunnels under the Thames ameliorate upon this method acting by pressurize the air in front of the shield to try and stop swamp during twist .
Tunneling shield are still used today , but are or else cylindrical and tend to be made out of steel , which is also used to make the tunnel ’s support rings . New variations also make use of hydraulic diddley to push the carapace forward , but when it ’s not locomote the area in front of the shield can be accessed via a door . To protect those who go out to work there , shields also feature a protective cowl .
Tunnel boring machines
Of course , labour through soft earth is one matter – boring through subaqueous rock is another thing totally . That ’s where New technology has changed the game , in the form oftunnel boring machines(TBMs ) , which were used in the building of the Channel Tunnel .
TMBs have a function similar to the tunneling shield , but in this case , a mechanical spinning cutting chief , rather than human force , is used to dig through the rock in front . It does this by exert stress on the rock , which causes it to fracture . And rather than people having to lug the debris out of the way , the fractured rock is taken back on a conveyor belt .
A total of 11 TMBs were used to moil out the three 56.3 - kilometer ( 35 - mile ) long tunnels ( yep , there’smore than one ) , which in their underwater stretch , are found 45 time ( 148 feet ) below the ocean bed .
Immersed tube tunnels
With the late method , the burrow wall are reconstruct as digging goes , but that ’s not the only way to do it . There ’s alsoimmersed tube tunneling , a proficiency build up by American engineer W.J. Wilgus .
Thismethodinvolves making the tunnel elsewhere first , make multiple prefabricate segments , whilst a trench is dredge from the river or ocean floor where the tunnel is designate to be . The segments are then float to the area , and sunk into place , after which the water is emptied from them , and dig up material is placed over the tunnel to bury it and restore the bed .
