How do you dig a tunnel without it collapsing?

Because we dig while reinforcing them. Once a tunnel is dug, the walls are sprayed with concrete and immediately hardened. Also, steel frames called steel support and steel rods called rock bolts are used to reinforce the tunnel so that it can be dug without collapsing.



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Installation of Rock Bolts for Extra Support: Another technology used in stabilizing tunnel portals is the installation of rock bolts. These are metal bars placed in the tunnel's walls and ceiling, providing extra support and improving the structure's overall stability.

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Although this is also seen to a certain extent in bridges, it is not to the extent seen in tunnels. Events such as earthquakes and floods, which are the major causes of collapse of other structures, account for only about 10% to 20% of all tunnel collapses.

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In cooperation with Rönesans Holding, the Heitkamp Construction Swiss GmbH tunnel and railroad construction specialists constructed the world's longest and deepest tunnel, the Gotthard Base Tunnel. This 57 kilometre-long tunnel lies at a depth of 2,300 metres.

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The Laerdal Tunnel in western Norway is the longest road tunnel in the world. It takes about 20 minutes to pass through the tunnel. Brightly colored lights placed every six kilometers help drivers stay alert.

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