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Three Gorges Dam

Three Gorges Dam

Unread postby Devil » Wed 25 Aug 2004, 06:54:27

The Virginina posted this in a different thread:
And contrast this with the other famous "mega project the thee gorges Dam" link Here's what happnes when you don't cool the concrete correctly (ice or water pipes as some comments suggest) IT cracks, badly: link So 1 Km of pure concrete? Up up and away?

I visited the dam site a couple of years ago and seen a lot of what is there, both upstream and downstream. The first link above is partial fact. The second link is just male bovine excrement with most of the posts displaying total ignorance of the project.

So, what did I find?
1. There is a risk with this, as in any major energy project. In this case, the risk is aggravated because the Yangtze flows through the gorges which were formed by a seismic fault. No earthquakes of > Richter 5 have ever been measured in the region and the dam is built for Richter 6+, so there is theoretically an order of magnitude of safety built in.
2. Water is incompressible, so that the shockwave of an upstream earthquake hitting the dam may be more disastrous than an earthquake at the dam site itself.
3. It is impossible to calculate the effect of an extra 60 billion tonnes of water on the seismic balance and this weight may be sufficient to trigger an earthquake.
4. The gorges themselves are formed from mainly friable sedimentary rocks. There are many places where it is evident that enormous chunks of mountain have, in recent geological history, broken off and fallen into the river. In fact, I witnessed a small landslide (I have photos). A large one could cause a surge wave which could overflow the dam and probably cause it to rupture.
5. Two large HE dams about 100 km N of the site burst in the latter half of the 20th c. (I can't remember the exact date) causing the death of an estimated 250,000 persons (official figure is 75,000), due to weather conditions causing an overflow. These were also correctly built and engineered dams.
6. The city of Yichang is ~20 km downstream from the dam, with a population of ~ 2 million. If the dam burst or overflowed, for any reason, the population would be wiped out. Wuhan is a major city (>7 million) 100 km or so downstream. Some of the population there could be evacuated. Jingzhou (6 million) is halfway between these, but not on the Yangtze, although in its flood plain. My guess is that a burst would kill >10 million in Hubei Province alone.
7. There is another risk, totally unrelated to a dam burst. China's largest city is Chongqing with a population of 31 million. Its sewage flows, untreated, into the fast-flowing Yangtze, where it decomposes rapidly aerobically. It is at the head of the retention lake. As the river slows down, the sewage will fall to the bottom as organic silt and it is estimated that a layer some 10 m thick will form in the gorges within a decade. This will decompose anaerobically, forming vast amounts of methane gas. Some of this will bubble up harmlessly (except that methane is a bad greenhouse gas causing climate change). Experts have stated that the pressure of 180 m of water above it will cause it to crust before decomposition is complete, forming vast reservoirs of methane which will grow and eventually burst. If this happens near a town, such as Wushan, on a calm day, a gigantic explosion could occur, as the humid gas would be held in by the gorge walls, rather than spread out. Where you have habitations, you have sources of ignition. At the best, the river will become very smelly from the quantity of raw human waste stagnating in the dam lake, probably with disease-bearing organisms. It should be remembered that the cities like Wushan have been rebuilt from current river levels to form a new shoreline 180 m higher.

I'm not mentioning the catastrophic human, agricultural, cultural and archaeological issues resulting from this terrible construction.
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Unread postby Guest » Wed 25 Aug 2004, 07:18:40

Kronos,

Thank you for the real life observations.

I had no idea about those other problems. They are serious, many could be overcome by dredging, better sweage management and inspection of the dam on a daily basis....

others are more fundemental:

Such as the sedimentary rocks you mentioned, and the fact that we only have a 1 magnitude of safety "built in"..while exponentialy this is a huge factor, how do we know that 1 or more above the 6.0 wont happen in the next 50 years or so... Granted 7.0 quakes are rare, but they do happen. So little of qauke history is actualy recorded acurately, especialy in rural areas. How can we be so sure thart a >6.0 has not happned in the last 500 years?

As for the "Freerepublic" article...

I will agree that most of the posters were just making fun of the Chinese, or not up to speed on exactly what is happening over there

Do you think the cracks that appeared on the dam are insignificant? My reason for posting about the three gorges was to compare to the Solar tower that is supposed to go 1KM high in NSW, Austrtalia...

Is it true that concrete makes its own heat and this can cause cracks, and that the Hoover dam has pipes w/ cold water still flowing through it? (or even had at one time?)

Where did China go "wrong" that there would be such cracks before the resivour was even filled? Or is this "normal".[/quote]
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Unread postby gnm » Wed 25 Aug 2004, 07:42:31

concrete definitely makes its own heat as it cures but I couldn't speak to whether or not this would require cooling pipes on such a large volume...

-G
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Unread postby Devil » Wed 25 Aug 2004, 07:56:32

Anonymous wrote:Kronos,



That ain't me!

Anonymous wrote:I had no idea about those other problems. They are serious, many could be overcome by dredging, better sweage management and inspection of the dam on a daily basis....


Dredging sewage 180 m deep ain't easy and must be mighty smelly! I agree that sewage treatment would alleviate some of the risk, but let's not forget that the catchment area has a population the triple or more of Chongqing itself. The dam is monitored constantly by laser metrology and satellite.

Anonymous wrote:
Such as the sedimentary rocks you mentioned, and the fact that we only have a 1 magnitude of safety "built in"..while exponentialy this is a huge factor, how do we know that 1 or more above the 6.0 wont happen in the next 50 years or so... Granted 7.0 quakes are rare, but they do happen. So little of qauke history is actualy recorded acurately, especialy in rural areas. How can we be so sure thart a >6.0 has not happned in the last 500 years?


I'm not over-worried about the direct effects of an earthquake, so much as the indirect effects, such as half a mountain falling into the lake: this could happen with a mild tremor acting as the last straw. Remember that dam burst in N. Italy a bit over 50 years ago when several thousand in a remote valley got killed with just this. The Mattmark disaster in Switzerland killed about 30-odd workers building the dam above Saas Almagell in 1965 or thereabouts. The lake was only about 1/5 full but a small chunk of glacier fell into it.

Anonymous wrote:
Do you think the cracks that appeared on the dam are insignificant? My reason for posting about the three gorges was to compare to the Solar tower that is supposed to go 1KM high in NSW, Austrtalia...

Is it true that concrete makes its own heat and this can cause cracks, and that the Hoover dam has pipes w/ cold water still flowing through it? (or even had at one time?)

Where did China go "wrong" that there would be such cracks before the resivour was even filled? Or is this "normal".


It is probable that the cracks are insignificant and, in any case, could be filled by high-pressure injection. The solar towe would be guyed steel, so cannot be compared. I'd imagine the section would be tapering to provide the required compressive and lateral strengths.

Yes, the chemical reaction as concrete hardens is decidely exothermic (never cast a concrete slab with rubber boots on while vibrating it???). A "strong concrete" (ie with too much cement in the mix) will always crack. A good engineer will always specify the weakest mix which will hold together to do the job and rely on the reinforcement for the strength. I don't know about the Hoover dam: it's possible. In very large masses, it may take years for the reaction to effectively finish; it's an exponential decay, asymptotic to zero so, theoretically, concrete never sets!
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Unread postby Geingreen » Wed 25 Aug 2004, 12:17:51

on the enviromission.com.au web site they say the Tower will be built of reinforced Concrete, not steel.

Maybe steel was the original plan.
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Unread postby Ender » Sat 28 Aug 2004, 06:50:25

gnm wrote:concrete definitely makes its own heat as it cures but I couldn't speak to whether or not this would require cooling pipes on such a large volume...


While it cures. Not once it's set.

The Hoover Dam had to be built piece by piece for this reason, and yes, cooling pipes were used during construction. You can't pour one mass of concrete in one hit like that - it gets too hot and tends to fracture.
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3 Gorges

Unread postby Devil » Thu 09 Sep 2004, 12:09:53

http://www.chinadaily.com.cn/english/do ... 373187.htm

Thank God, the dam has withstood this year's threat, less than one year after closure. But, as the water level in the reservoir rises further, will it cope with repeated stress of this magnitude?
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Unread postby gnm » Thu 09 Sep 2004, 12:23:42

The Devil is Thanking God!

8O


-heheh

-G
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Unread postby Terran » Fri 10 Sep 2004, 23:51:17

Thank God, this is over. I find it pretty hard to believe to try to tame one of the largest, and longest rivers in the world.
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Unread postby The_Virginian » Sat 11 Sep 2004, 17:07:24

Well they claim it is one of those once in 100 year type floods....

Hmph....

We shall see....
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Unread postby Devil » Sun 12 Sep 2004, 03:16:33

That's what they said 2 years ago.

I have seen the dam and I've seen the Yangtze for about 300 km upstream (and 30 km downstream). Believe me, I'd feel safer next door to Chernobyl than downstream from that dam. The dam itself is built according to the best engineering standards, but the geology of the region isn't. It is a catastrophe waiting to happen and it will happen. Maybe next year or in a decade or in 50 years but the 2 million-odd inhabitants of Yichang (20 km downstream) would not have a snowball's chance in hell of surviving, not to mention at least 12 million others in the Province, some of whom may be able to escape in time.
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Hong Kong fisheries paralyzed

Unread postby Barbara » Tue 12 Oct 2004, 03:31:07

This is the first economy to be heavily hitted by oil prices:
http://www.asianews.it/view.php?l=en&art=1659

What do you have to say, lowem?
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Unread postby lowem » Tue 12 Oct 2004, 03:52:36

Peak Fish too, huh.

I'd say this is one Scene out of many Acts in "The Rise and Fall of Fossil Society". And here we are, just about halfway through the show ...
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Unread postby seb » Tue 12 Oct 2004, 06:58:05

In Japan fishery is down too but the reason is that 9 typhoons came here this year. All time record.

Now people are talking about a major climate change which lead to this upward trend in typhoons. So you can choose : either people don't talk about true problems or when they talk about it this is always with stange argumentation. 9 typhoons so the climate has changed. This is supposed to be the ultimate proof of global warming. You can read this in the japanese news paper every day. Save science!!! And teach journalists the basics...
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Unread postby backstop » Tue 12 Oct 2004, 07:50:59

Seb - If you don't see a record 9 typhoons so far this year as an evidence of climate destabilization, I suggest you have a look at the equally extreme weather that has been occuring with increasing frequency around the globe in the last few years.

As for your call to "Save science" I'd point out that for thirty years science has been up against the most powerful lobby on the planet, the oil industry, in trying to get the issue addressed. The evidence of man-made global warming is now considered irrefutable by governments around the world, including that in Washington.

If I sound passionate on this, it is because I know of the millions who are dying each year of malnutrition and the ailments of poverty due to unprecedented weather impacts on subsistence farming. The longer we leave the necessary global response to global warming, the more genocidal that death-toll will become.

regards,

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Unread postby seb » Tue 12 Oct 2004, 08:08:17

backstop,

I do not deny the (very) bad influence of humanity on the cllimate. I am already convinced about this. What I say is that even if the conclusion is good it is sad to see that many people see a very local event as the proof of global warming.

The Japanese had 9 typhoons this year so they think climate is changing. But if there are only 2 next year they will think things are ok then. People are very slow to react to a global trend, they only see the local noise. And newspapers amplify the noise very strangely...

I am a scientist (mathematician) and I work on numerical simulations applied to physics (nuclear fusion). We have to be very careful with all the models we have about such complex and nonlinear systems like earth climate. We have only a rough idea about what is going on. This does not mean it will not be a disaster, nobody knows precisely. Anyway I really laugh when people say : "if we can not prove, being 100% sure, that a disaster is coming then we'd better do like it will not happen".

But 9 typhoons is not a proof about anything. I feel this is a shame to justify true scientific conclusions with non scientific stupid arguments. I think you will agree it : stupid arguments destroy the conclusion.

Sorry if I was not clear with my last post.
Seb

PS : the number of typhoons is roughly constant every year. So if Japan had many, other contries had less. Right? So these people may think that the climate is better... :roll:
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Unread postby gnm » Tue 12 Oct 2004, 08:18:17

I am going to have to agree with the math man on this one... there is no proof that human influence is responsible even if subtle warming is happening. People tend to ignore that giant ball of fire in the sky - output has increased some and venus and mars have even warmed a bit.. historically co2 levels have been wayyyyy higher than now - did man do that too?

btw last year it was colder on average over nearly the whole US..

if you want to worry about manmade effects on the environment I would have to say chemical dumping - particularly endocrine reactive toxins... very nasty in very small amounts!

-G
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Unread postby backstop » Tue 12 Oct 2004, 08:31:31

Seb - I well agree about the perverse stupidity of the media's handling of the climate issue. In the UK we had a classic example last night.

14 years ago a serious lay-science book was published here (Hothouse Earth, by Dr John Gribben) that detailed the whole issue at a level for media and politicians to understand. It included detail of several of the positive feedback loops on global warming that have been accelerating ever since.

Last night the BBC Newsnight program interviewed the UK's cheif scientist (for about 3 minutes) and for the first time in 14 years the feedback loops got mentioned on the mainstream UK TV.

By the way, I wonder what it would take for you to transfer your professional skills from nuclear power to an energy resource that is both more creative and more appropriate for the global condition ?

The reason I ask is that Mitsubishi have some world-class development going on in forest-sourced methanol-production, and as far as I can find out they've yet to get a grip on the potential yield-patterns and diverse benefits of the optimum form of forstry, which is known as "Coppice."

regards,

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Unread postby stayathomedad » Tue 12 Oct 2004, 11:06:50

uhh, I do not believe in global warming per se, as in man-made. folks forget that there was a time when they had wineries and dairies on greenland....just a mere 1200 years ago. ever thought about where the name greenland for greenland comes from?

our atmosphere is so heat absorbent, mainly due to the water in it, that the natural water in the air absorbes almost all thermal energy...yes the protical 'greenhouse gas' is plain old water.

cyclones, may refer to them as hurricanes or typhoons, are periodic as well. it is just that we went though a 40 year periode which was slow, and they pick up. in the atlantic they are tied in with the trade winds, the winds which brought the settlers here and the merchandise, and the goods back to europe. so when those trade winds do well, then the hurricanes do as well. interesting discussion on that on the national hurricane center web-page.

cheers
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Unread postby stayathomedad » Tue 12 Oct 2004, 11:11:35

forgot about fishing: I like that news. simply because all the fish stocks are overfished.....I am starting to think that the end of cheap oil may actually be the saving grace for our planet. I am starting to take a very positive attitude about this. Things will get better, there will be more jobs, as we need the crafts and trades again, things will matter again.

So maybe I chance my signature to: There is a light at the end of the tunnel!
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