"Chad Irby" wrote in message
. com...
In article ,
"Kevin Brooks" wrote:

"Chad Irby" wrote in message
om...
In article ,
"Kevin Brooks" wrote:

If *your* interpretation of that is that it requires a weapon
capable of breaching a massive dam like Three Gorges, then you
need a reality check and some remedial reading comprehension
work. That dam is over 180 meters tall, and contains some 26 plus
*million* cubic meters of concrete (more than *twice* the mass of
the world's previous record holder). It is designed to handle a
7.0 Richter scale event. Reality check time--what conventional
weapon do you know of, or can you even conceive of, that could
*breach* a structure of those massive dimensions? Answer--none.

Actually, the answer is "a pretty big one, but not as big as you'd
think."

I believe your analysis is a bit faulty in this case; see below.

While I'm *sure* yours is, from the assumptions you made about
thickness. Height and overall mass is all well and good, but stress,
construction and *thickness* are the important issues for a Wallis-type
bomb. The Three Gorges, while very tall and very long, isn't as thick
as you seem to think.

Actually, the only guage I have for thickness is the claim you made that the
structure was around twice as thick at the mid-point as the Rhine dams
mentioned. Plus knowing the height of the structure, it is easy to surmise
that the base dimensions have to be pretty darned big themselves to resist
the massive moment resulting from the hydrostatic load. Of course, we could
get a SWAG by taking the volume of concrete (known), the height of the
structure, and then figuring the likely bottom "thickness" (as I believe you
have called it)...let's see, 26 million cm with a max height of 185 meters
and a length of about 2300 meters, gives us a likely bottom measurement in
the area of about 122 meters, assumeing a uniformly decreasing cross
section as you go up (yeah, I know that is probably not the case, but it
will be close enough, and I have yet to see anything that actually provides
the cross sectional dimensions of the dam as built).

The Three Gorges is certainly very wide, and very tall, and quite
thick at the base, but if you hit it about halfway up with a full
reservoir, you could breach it with a moderately-large explosive
package, since it's only about twice as thick at midpoint as the
Mohne dam was at the point the Wallis bomb broke it.

The Wallis bomb was apparently good against a target that did not
exceed about 50-feet thickness at the point of detonation (see:
www.arnsberger-heimatbund.de/moehneattack.html ). The Mohne and
Eider dams challenged the ability of the Walls bomb to do the job,

Actually, it was the *placement* of the bombs that caused the issues.
One bomb, well-placed, was more than enough in each case. Their aiming
system was a couple of spotlights and a piece of wood with nails in it...

and as you note the Three Gorges is substantially more massive (and
you may be a bit low on your estimate--remember that the dam crest
sits about ten meters above the flood stage overflow water profile,
from what I have read).

"Substantially" being about twice, at about the halfway point. Which is
why I mentioned a much larger weapon with a much more powerful
explosive. Fired off at a deeper location, double the water depth,
double the tamping effect, placed directly against the surface, you
should be able to get at least a factor of four more destruction, which
would do a lot to the twice-as-thick wall of the Three Gorges at about
halfway down.

Let's see. Since the max ordinate for the dam in terms of upstream fill is
supposed to be only about 175 meters, from what I have read, you halfway
dimension would apparently be, based upon that 122 meter estimate above,
something like 57 meters--let's be generous and assume a more favorable
number for you, of maybe 40 meters (reflecting a more realistic actual cross
section). Which last I knew was quite a bit more than 100 feet--more like
125 feet?

Not sure that your everything-increases-linearly-as-you go-down concept is
the most accurate way of describing this situation. By that reasoning one
could kill submarines at great depth with mere handgrenades, right?


Since the explosive for the Wallis bomb was 6600 pounds, you could
probably knock a big hole in the Three Gorges with a ten or twelve
ton bomb of more-aggressive explosive,

Now we are getting into fantasy land (I know, that is a place where
Henry
usually enjopys playing, but still...).

Nope. As I mentioned, it's certainly a feasible thing to do. Not
airdropped (as I mentioned further into my post),


Then you just made it infeasible in terms of being strike weapon, which is
what this thread is all about. We are not discussing the possibility of
driving a trainload of HE to the dam and carefully assembling and placing a
massive charge in the reservoir--we are talking about military strike
options.

but it's not hard at
all to place large items by hand, if suitably ballasted. A modern high
explosive would do a *lot* more damage than anything they'd try to use
in WWII. A higher propagation velocity would *magnify* the effects
versus WWII high explosives.

What you are referring to is the Relative Effectiveness factor (RE), which
uses TNT, a WWII explosive if there ever was one, as the basis of
measurement (with a value of 1.00); C-4 had an RE of 1.34. But you have to
be careful here; C-4 does indeed exhibit significantly faster propogation,
and hence "brisance" (or "shattering effect") when compared to TNT, but if
you instead want to start looking at its other qualities, such as its
"heave" effect, you will find very little difference.


There are some concerns about the construction or the 3GD (they had
80 fairly long, two meter deep cracks form when they started
filling it).

OK, now you are arguing that the PRC themselves may have created a
potential future catastrophe in the making--plausible, but unlikely
IMO (a 2 meter depth crack is nothing if the thickness of the mass at
that point is seventy or eighty meters).

...except that the thickness you're talking about is only at the
*bottom* of the dam. It slopes in a *lot* on the downstream side to
about the halfway point, where it's less than 100 feet thick (the
upstream side is a vertical wall from top to bottom). A two meter depth
*surface* crack in concrete is almost certainly not the only crack
you've got in a structure that size (besides the 80 surface cracks they
know of, how many are there deeper in?).

Newsflash--concrete cracks. It is quite a common occurence. The real issue
is the roientation of said cracks; running vertically, no big deal.
Horizontally, you may have something to start worrying about.


China isn't famous for good construction practices, and average over a
hundred dam collapses per *year*.

A moderately paranoid person might also consider that the Chinese
government could be dropping these "Taiwan may attack dam" stories
in order to give them someone to blame when and if the thing lets
go on its own.

But the source induicated for this discussion is not the PRC, but a DoD
report that included some musings accredited to Taiwanese, with TG
merely
being offered as an example.

The original DoD report only mentioned that Taiwan might hold the option
to attack various high-value targets (like 3 Gorges) in China if the
Chinese invaded Taiwan (as possible strategies), but the PRC has already
made some very strong comments. There are other sources than the one
minor one that started this thread.

"It will provoke retaliation that will 'blot out the sky and cover up
the earth,'" according to one general in the PRC, quoted in a lot of
places (Reuters story, June 16).

Note that the Pentagon report on this was from last year. Why the
strong comments *now*?

Who knows? Who really cares, given that the Taiwanese don't have, and won't
be getting, any capbility of breaching said dam. Now, can they hit the
ancilliary structures and do a temendous amoundt of damage? You betcha--and
I'd be willing to bet that is the kind of thing that the PRC would be more
worried about.


The sort of thing that would destroy the Three Gorges wouldn't be
air-deliverable by Taiwan, but would be easy enough to assemble
upstream and place with divers.

That is one big puppy you are talking about smuggling into the PRC,
assembling, and then getting into place. Not exactly what I'd call a
reliable military strike option.

Actually, it's not really that large. A good-sized truck would hold it.
Or a few bribes to one or more PRC officers to get some stuff that's
already handy. Not to mention that there was probably a few thousand
tons of TNT used during the construction of 3G, and diverting a fraction
of a percent of that wouldn't be too tough.

Hell, unless the PRC has some *extreme* measures in place, it wouldn't
be that hard to put a *hundred* ton bomb of some sort in a boat, steer
it to the dam, and sink it with a depth sensor for detonation...

OK, now we are getting into true fantasy land. This discussion started out
about military strike operations, not John Wayne/Errol Flynn/Rambo
Supercommando operations. The psited case is for Taiwan to do this in order
to retaliate against a PRC invasion--and you see commandos, and boats, etc.,
running willy nilly about all over and around the dam, on land and water?
Come on, now...

Brooks


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