how do you build an underwater tunnel?

The oldest method of digging under water without running water is called a tunneling shield, and engineers are still using it today.
Shields solves a common but annoying problem, that is, how to dig a long tunnel through soft soil, especially underwater, without the collapse of the leading edge
Source: Job discovery;
Encyclopedia of Great Britain; Browne; Hewitt].
To understand how the shield works, imagine a coffee can with no lid, sharp at the bottom, with a few big holes.
Now, grab the opening and push the tin at the bottom into some soft dirt first to see how the dirt goes through the opening.
In the scale of a real shield, several people (
Nicknamed \"muckers\" and \"sandhogs \")
I will stand in the compartment inside the \"jar\" and remove clay or sand as the shield advances.
The hydraulic jack will gradually move the shield forward, and the staff behind it will install a metal support ring and then lining the shield with concrete or masonry [
Source: Job discovery;
Encyclopedia of Great Britain; Browne].
In order to prevent water seepage in the tunnel wall, sometimes the front of the tunnel or shield is pressurized with compressed air.
In this case, workers who can only bear a short period of time must pass through one or more gas gates and take preventive measures
Related Diseases [Source: Hewitt; Port Authority].
In particular, the shield is still used when installing public or water and sewage pipes.
Although the labor intensity is high, their cost is only a fraction lower than their huge sibling tunnel rig (TBMs)[
Source: Job discovery;
Encyclopedia of Great Britain; WGBH].
This is a multi-layer
Tall destruction engine capable of chewing hard rock.
Rotate a cutting head in front of it, a huge wheel, brush hair with Stone
Break the disk and use a spoon system to lift the hit Rock and place it on the outbound conveyor belt.
Swinging a trimmer at the back of the cutting head, this is a rotating assembly that builds the tunnel lining at the rear of the TBM.
In some large projects, like tunnels, independent TBMs will start at both ends and drill holes into the center point, keeping them on [track] using complex measurement methods
Source: Job discovery; Coleman et al. ; WGBH].
Drilling in hard rock can produce a large degree of self.
Support the tunnel and TBMs move forward quickly and relentlessly (
Some tunnel machines can drill 250 feet or 76 metres per day).
Below, TBMs are easier to break down than used Jaguar, dealing with worn, cut or highly engaged rocks ---
So they\'re not cracked as fast [sources: WGBH; WGBH].
Fortunately, TBMs and shields are not the only games in town.