How do you build tunnels underwater?

Question

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Answer 1

There are several ways to build tunnels underwater.

One way is to build sections of tubes in advance, float them into position using tugboats, sink them, have divers go down and seal the sections together, and then pump the water out.

A more traditional way is to dig a tunnel far enough below the sea bottom that the rock over them keeps out the water. It's kind of like digging a mine,

If the rock or soil isn't able to keep out all the water while the tunnel is being dug, sometimes it's possible to pump compressed air into the tunnel, so the pressure inside the tunnel is greater than the water pressure outside, and have workers seal the inside of the tunnel with a concrete or steel lining.

Answer 2

Here's one way....

Immersed Tube Technique
The immersed tube method, a version of the cut and cover technique, is a cheap and easy way to construct a tunnel under water -- and it's generally the fastest way.

Here's how it works:
Dredging machines cut a trench in the riverbed. Then one by one, preassembled, watertight tubes are floated out and lowered into place over the trench. Divers bolt each segment together to form the complete tunnel. The tunnel is then covered with a steel-and-concrete casing to prevent the tunnel from floating and to protect it from damage caused by passing ships. Underwater tunnels around the world, including Hong Kong's metro tunnel system and San Francisco's Bay Area Rapid Transit tunnel, were put together like this.

Answer 3

There are several ways to build a tunnel underwater. It can be built underwater and pumped out, or it can be built above ground and assembled underwater. There are a variety of concretes that will harden underwater. Most of the work would have to be done by divers.

Answer 4

An Immersed tube is a kind of underwater tunnel constructed using segments built elsewhere, floated and sunk into place, then welded together to form the tunnel. This method can be considerably cheaper than excavating through rock, and is more resistant to earthquake damage. The trade off is that immersed tubes are more vulnerable to terrorist bombings than excavated tunnels, since less explosive force is necessary to breach their walls than would be required to penetrate the roof of a tunnel through rock.

Answer 5

Underwater tunnels...
are particularly tricky to construct, as water must be held back while the tunnel is being built. Early engineers used pressurized excavation chambers to prevent water from gushing into tunnels. Today, prefabricated tunnel segments can be floated into position, sunk, and attached to other sections.

Answer 6

This Site Might Help You.

RE:
How do you build tunnels underwater?
One of the gracious Yahoo! Ask the Planet headquarters hostesses from the Hard Rock Cafe just asked this question of the Brainiacs in the big purple brain in Times Square, and we thought we would invite you all to help us out with this one. Who knows the answer?

Answer 7

You either use

a)cofferdams (which block out the water in certain areas, and allow you to work on the floor of the river/lake/bay)

or

b)you do what they did with the footings of the brooklyn bridge in new york, where they built a massive wooden box, sunk it to the bottom of the river, and then pumped air into it so that the water was pushed out. Then they dug down to a certain depth, poured concrete, and removed the wooden box (I suppose you could do this to build a tunnel

or

c)you prebuild sections of the tunnel above water, then sink them in the water, assemble them using divers, and then pump the water out. They did this with some tunnel in or near Seattle.

Answer 8

What constitutes a tunnel is not universally agreed upon (wikipedia:Tunnel). But, if you want to build an underwater passageway, you can use cofferdams to hold out water, then build the passageways, or you can use prefabricated segments and place them according to blueprint.

Answer 9

well if you watch those shows on dicovery or discovery times or science channel you can see for yourself ! Extreme engineering is an excellent show as well as Mega Structures.
OF the ones I have watched - they pre-fab the tunnel structure - float it into place and sink it. It's assembled underwater by divers, and then the workers come into to the tunnel to do the inside. Shot-crete is pretty popular these days for quick concrete methods and I have seen them shoot this on the interior of the tunnel walls.

Answer 10

there are two ways to build tunnles under water.

first you could use a tunnle digging machine, which is a huge machine that bores through rock, just as you might expect.This is how they built the tuunder the english channel.

Two you could pound cement piles into the ocean floor, then sink prefabricated sections of the tunnel underwater, attach them to the piles, weld them together, then drain them, and do everything else, such as paving, ventalation,etc.