Underwater tunnels
June 11, 2007 11:20 AM   Subscribe

Tunneling under water: how do they plan how deep they need to dig?
posted by cgs to Science & Nature (2 answers total) 1 user marked this as a favorite
 
Best answer: Assuming the tunnel is being run underneath the [sea, lake river etc.] bottom,
The load bearing capacity of the rock is known, or will be calculated using geotechnical surveys, you can calculate how much rock you need to withstand the pressure difference between the (roughly) 1 atm pressure inside your tunnel and the pressure of the water above. Of course your tunnel design effects this as well, thickness of walls etc, plus a healthy safety factor.
I'm not a civil eng, so I can't give you details, but that is an educated guess..
posted by defcom1 at 12:17 PM on June 11, 2007


Best answer: I am not a mechanical engineer, but I'm pretty sure that they figure this out by drilling into the earth along the proposed tunnel route and take core samples. This lets them know how deep below the sea bed they need to tunnel in order to find dry, stable earth or rock.

Keep in mind, though, that some underwater tunnels are just water-tight tubes sitting on the floor of the river/harbor/sea. They don't always have to dig.
posted by autojack at 12:18 PM on June 11, 2007


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