Building Immersed Tube Tunnels

The Most Implausible Tunneling Method
Practical Engineering

These guys are insane. Look at the organization skills required, you have to get bunches of experts to cooperate on design and techniques. You need bunches of skilled people. Not every one has to be an engineer, but ever job is critical. The guy who connects the hydraulic hoses, or shoot, even the guy who checks whether the bobby pins are correctly installed in the hitch pins. 'Bobby pins' is my term, but it got us there.

Clevis with large pin installed and bobby pin inserted in the large pin

'Hitch pin' seems to be the preferred term.

Anyway, there are, I think he said, over a hundred of these things around the world. I don't think I ever heard about this technique before. Well, I probably heard it mentioned on a newscast that the project utilized immersed tubes, and that doesn't really tell you much. I like his analogy comparing installing one section of tunnel with docking a spaceship. 

These projects are always huge gambles. The results when they are successful are great, but all big projects can be derailed by unforeseen events. These events can be minor or they could result in the project being canceled and all money spent to this point is just gone. Well, it's not a complete waste, at least the workforce will be willing to go to work on another project, should you come up with one. If they didn't get paid for their work so far, they wouldn't be so likely to go to work on a new one.