Anyone Else Fascinated by "Mega Engineering" Projects?

[RoJoHen]

I live on the Mississippi River, and we have a large bridge that connects Illinois to Iowa. Unfortunately, with all the commuting back and forth during rush hour, the bridge has a habit of getting extremely congested. Over the next 5 years or so, they are planning to build a new, much larger bridge to accommodate the traffic. It's not the craziest engineering project ever, but I'm still pretty interested to see how they do it.

 

[SmoothieX]

The interesting part is how they will need to keep the old bridge open while building the new one, then re-route it over the new span.

The TZ Bridge has been falling apart for years and there has been talk of replacing it forever. We all joked in college that we'd all be working on the new one after graduation. It only took 10 years but they are finally getting going on it.

I know they can't justify the added expense, but I'm annoyed there is no rail component to it. There are commuter rails on both sides of the river with no connection.

 

[gturner]

Suppose you built a series of self-supporting bridges out of carbon fiber or spectra that were only supported at their ends (which of course spread out and get bolted to concrete supports toward the sides. You make them slightly elevated so you drive up a slight ramp, across the bridge, and down the other side. Since they're vastly lighter than an existing bridge, they are transportable, and you lease them to companies and governments conducting criticial repairs to small, heavily traveled, existing bridges (specifically overpasses and such). You set the mobile high-tech bridge over the existing bridge, which it clears by about 8 feet to allow road crews to work underneath while traffic flows overhead on the carbon-fiber bridge. When work is completed the high-tech bridge gets moved to the next repair project.

Perhaps you move the temporary bridges with either airships or helicopters, maybe providing mounts so the rotor sections of several Sikorsky skycranes can be attached to booms on the sides to make a four or six-rotor flying bridge. Then you look at how many repair projects each size bridge can handle, the number of projects it can handle per year, the construction cost of the high-tech aerospace bridge, the transport and installation/removal costs, insurance, and how much contractors and cities would pay to lease one, per project.

 

[Mr. Laser Beam]

You don't see the value in being able to take a train - a train - from New York to London? In ONE HOUR?

No, not when plane travel is easily affordable.

Air travel these days is a total drag and everyone knows it. (And it is NOT affordable, unless you take one of those cheap-ass airlines that charges you for carry-on bags and doesn't even have reserve seating.) Wouldn't you really rather get on a train? Much less hassle.

Even with HS1 leading from St Pancreas to the Euro-tunnel now connecting up with the continental HS network, you can't even get from London to Paris in an hour.

Hell, I can't even get to London within an hour by train and I'm less than 100 miles from the capital.

With this transatlantic tunnel, you will.

 

[John Mason]

The transatlantic tunnel would not be possible due to the tectonic activity of the mid Atlantic ridge.... but the idea of vacuum tubes suspended fifty meters under the surface might bear merit...

 

[John Mason]

"You think I want to go into space! I don't even like to fly! I take trains!"

 

[Mr. Laser Beam]

I weep for the lost rail culture that we once had in the US. I admit I'm biased, because I love trains, but I wish more people did. There's nothing exciting or leisurely about getting on a damn airplane, and that has been the case even before 9/11. Train travel is a thing unto itself.

As for driving? Forget it. I fucking hate to drive. I wish I lived in a city with decent mass transit - I wouldn't even own a car then.

 

[DimesDan]

You don't see the value in being able to take a train - a train - from New York to London? In ONE HOUR?

No, not when plane travel is easily affordable.

Air travel these days is a total drag and everyone knows it. (And it is NOT affordable, unless you take one of those cheap-ass airlines that charges you for carry-on bags and doesn't even have reserve seating.) Wouldn't you really rather get on a train? Much less hassle.

Even with HS1 leading from St Pancreas to the Euro-tunnel now connecting up with the continental HS network, you can't even get from London to Paris in an hour.

Hell, I can't even get to London within an hour by train and I'm less than 100 miles from the capital.

With this transatlantic tunnel, you will.

What a Moronic comment. Even with our fastest trains, it would take hours to transverse that distance.

I'd rather get on a 747, Airbus A380 or Concorde (if it still flew) and fly between here and North America than go underground - under the Atlantic Ocean for that matter.

Who would you get to pay for such a white elephant anyway? I sure as hell don't want my tax money paid towards this, if it were remotely possible.

 

[MacLeod]

Well if a transatlanic tunnel was feasbale in order to get those kinds of speed to traverse the distance in an hour or so. It would have to be a vacumn and use something like mag-lev technology so there is no friction to slow the train down.

 

[Roger Wilco]

Air travel these days is a total drag and everyone knows it. (And it is NOT affordable, unless you take one of those cheap-ass airlines that charges you for carry-on bags and doesn't even have reserve seating.) Wouldn't you really rather get on a train? Much less hassle.

A regular train maybe, but there would be nothing leisurly about riding a train in a transatlantic tunnel either. Can you imagine what a target that would pose for terrorists or just assholes?

 

[scotpens]

"Deep-sea colony"? Just, why?

Because it would be so damn cool!

 

[Mr. Laser Beam]

Air travel these days is a total drag and everyone knows it. (And it is NOT affordable, unless you take one of those cheap-ass airlines that charges you for carry-on bags and doesn't even have reserve seating.) Wouldn't you really rather get on a train? Much less hassle.

A regular train maybe, but there would be nothing leisurly about riding a train in a transatlantic tunnel either. Can you imagine what a target that would pose for terrorists or just assholes?

Terrorists wouldn't have the resources to get down that far.

Besides, you can't just chicken out and refuse to build anything at all just because terrorists MIGHT try to get at it.

 

[gturner]

I've almost responded a couple times on the Atlantic tunnel idea, but it's so unworkable that I didn't bother.

It would involve boring through basalt, not chalk, and for that alone the costs per mile would be roughly 10 times higher than the Chunnel. But the Atlantic isn't shallow and it isn't short. The depth, which averages about ten times the collapse depth of a nuclear submarine, means the tunnel walls will have to be very thick steel, probably about 30 inches for a 30 foot inner diameter. That means you'll need about 1.2 billion tons of steel, which at current world production would be 850 years worth. So not in our lifetimes is an understatement.

The other problem is that the tiniest crack or hole at those pressures is devastating (as the Thresher accident board found out with high pressure water jet experiments), and the entire tunnel could flood about as quickly as water can be driven at those pressures. Repairing the damage could require a thousand mile journey in a submarine that can withstand ocean basin pressures, and that's just to look at the giant hole. With the thousands who were almost certainly killed while transiting when the rupture occured, would anyone even bother to fix it?

If we're ever going to build a tunnel to Europe, it's going to go up to Alaska and across the Bering Stait and through Siberia and on to the Urals. Crossing the Bering Strait will be a mega-engineering project in itself.

 

[MacLeod]

Air travel these days is a total drag and everyone knows it. (And it is NOT affordable, unless you take one of those cheap-ass airlines that charges you for carry-on bags and doesn't even have reserve seating.) Wouldn't you really rather get on a train? Much less hassle.

A regular train maybe, but there would be nothing leisurly about riding a train in a transatlantic tunnel either. Can you imagine what a target that would pose for terrorists or just assholes?

Terrorists wouldn't have the resources to get down that far.

Besides, you can't just chicken out and refuse to build anything at all just because terrorists MIGHT try to get at it.

Deciding not to build somehing because it might suffer a terrorist attack. Means the terrorist has won.

 

[Mr. Laser Beam]

^ Exactly.

It would involve boring through basalt, not chalk, and for that alone the costs per mile would be roughly 10 times higher than the Chunnel. But the Atlantic isn't shallow and it isn't short. The depth, which averages about ten times the collapse depth of a nuclear submarine, means the tunnel walls will have to be very thick steel, probably about 30 inches for a 30 foot inner diameter. That means you'll need about 1.2 billion tons of steel, which at current world production would be 850 years worth. So not in our lifetimes is an understatement.

Like I said, the tunnel will not actually be bored into the ocean floor, but rather suspended about halfway up from it.

 

[gturner]

Okay, that gets you down to needing 400 years worth of world steel production, but it does eliminate the need for boring, which would have to be done at full sea-floor pressures to prevent blowouts at the face. But then you get the problem of anchors that are literally miles high, which might have to be in compression because at those depths I don't know if a steel pressure vessel would be positively bouyant, and concrete or ceramic pressure vessels might not take the tensile stress of large current-induced side-loads. I'd still estimate a construction cost of several hundred trillion dollars, which will probably limit ticket prices to the million dollar range - to save a few hours on an airplane.

There's another problem with any sway or flex in a high-speed (ie. mach 10) tunnel, which is that if the tunnel shifts by a couple feet in several miles of run, the side-impact loads on the passengers are potentially fatal. So either the suspended tunnel has to be extremely stiff or extremely well supported (which is very hard when the supports are themselves miles long), or the train has to travel at fairly conventional speeds (very low mach or subsonic).

Given that a purely land route the other direction (with a dip through the Bering Strait) doesn't have these constraints, you'd almost certainly get from New York to London faster going the other way, strange as that sounds. Heading west at mach 7 beats heading east at mach 1.

 

[Knight Templar]

I thought the idea of a "suspended mag lev tunnel" across the Atlantic was for a "tunnel" (actually a tube) which was about 1,000 feet or so beneath the Atlantic surface.

No ship ever built or proposed, or even suggested would be prevented from passing overhead.

IIRC, even proposed 1 million ton supertankers only have drafts of about 100 feet

 

[RobertVA]

Suppose you built a series of self-supporting bridges out of carbon fiber or spectra that were only supported at their ends (which of course spread out and get bolted to concrete supports toward the sides. You make them slightly elevated so you drive up a slight ramp, across the bridge, and down the other side. Since they're vastly lighter than an existing bridge, they are transportable, and you lease them to companies and governments conducting criticial repairs to small, heavily traveled, existing bridges (specifically overpasses and such). You set the mobile high-tech bridge over the existing bridge, which it clears by about 8 feet to allow road crews to work underneath while traffic flows overhead on the carbon-fiber bridge. When work is completed the high-tech bridge gets moved to the next repair project.

Perhaps you move the temporary bridges with either airships or helicopters, maybe providing mounts so the rotor sections of several Sikorsky skycranes can be attached to booms on the sides to make a four or six-rotor flying bridge. Then you look at how many repair projects each size bridge can handle, the number of projects it can handle per year, the construction cost of the high-tech aerospace bridge, the transport and installation/removal costs, insurance, and how much contractors and cities would pay to lease one, per project.

About seventeen years ago a Virginia USA bridge was replaced on the same site with less than two weeks closure.

While the pier bases were being enlarged on the original bridge site the new bridge was built on temporary pier bases, complete with signage, lighting, lane markings and signals. When the new bridge was complete the old bridge was floated away for demolition on big barges. The new wider bridge was then barged into position (in a few large sections) and the barges carefully flooded enough to lower the new bridge sections onto the the enlarged original pier bases. Old and new bridges have rotating sections that open to allow ships to pass (Navy munition depot upstream). http://www.pbs.org/wgbh/buildingbig/wonder/structure/george_p_coleman.html (click the thumbnails to see photos illustrating how the bridges opened/open and one of the new sections being floated into place)

A similar procedure is planned for the lift span of a smaller Virginia draw bridge. The new lift towers have been being built straddling the stationary sections of the old bridge, which has been subject to some weekend and overnight closures while steel structural columns and beams were craned into position.