Big Trouble in Little China

[Chris Coles]

Re: Big Trouble in Little China

Personally, if I have no information or the source is unreliable, I always assume the worst case scenario.

At the end of the day, we can always rely upon the professionalism of NASA. https://earthobservatory.nasa.gov/im...s-spill-water? There is no sign of anything wrong with the Three Gorges dam.

[touchring]

Re: Big Trouble in Little China

Those “after” photos are ridiculous.

I wonder if a better comparison than ‘before/after’ photos might be with Fukushima’s nuclear plant, where everything was fine until it wasn’t

In short, my concern is around non-linear communication of escalating bad news, which is a real risk due to both long-standing cultural and more recent communist cult of infallibility reasons.

Personally, if I have no information or the source is unreliable, I always assume the worst case scenario.

[lakedaemonian]

Re: Big Trouble in Little China

There's a lot of fake satellite photos showing the dam highly distorted which I read is impossible because concrete would have disintegrated if they could be seen distorted that way visually. I don't believe the dam would collapse just because of one flood, but if this flood repeats every year and along with some future seismic event, the lifespan of the dam could be reduced to maybe only decades instead of 100 years originally planned.

Read this from the state media. This was 30 June before the flood became really serious in mid-July.

Those “after” photos are ridiculous.

I wonder if a better comparison than ‘before/after’ photos might be with Fukushima’s nuclear plant, where everything was fine until it wasn’t

In short, my concern is around non-linear communication of escalating bad news, which is a real risk due to both long-standing cultural and more recent communist cult of infallibility reasons.

[lakedaemonian]

Re: Big Trouble in Little China

In 2009 a Russian hydro dam had a catastrophic failure of the power machinery. The dam structure as a whole stayed intact and held back the river. The power plant is just finishing repairs now, a decade later.

Here's some photos






If you haven't spent time in big hydro dams you might not appreciate the enormous scale of this structure.
In the rubble on the right, look at those yellow cranes. Those are big hundred ton cranes.
In the "before" picture, notice the circles on the floor. Those are the top covers for the round generators; the water turbines are a few stories below, down in the water.

Here's a shot of a generator rotor after the event. It's one of the circles on the floor. Notice the people standing on the rotor to get a sense of scale.
There is not much empty space or air in such a rotor. You can think of it as a solid chunk of copper and steel.
Hidden under it is the main drive shaft going down to the turbine. It's a solid steel shaft about 3 feet in diameter and maybe 30 feet long. Close under this rotor is a shaft coupling to disconnect it. The coupling is pretty close to the generator rotor, so the rotor stub shaft to the coupler might be eight or ten feet long.



Hydro generators turn at low speeds, this one turns at about 140 RPM. I would expect this rotor to weigh about 250 tons; that's 40 fully loaded semi trucks.

A rotor like this was the problem. I don't think it was this particular rotor because it looks like this one's still inside the ruins of it's stator.
But one of these broke free at speed. It bashed through the structure around it, and went dancing across the generator deck on it's stub shaft like some gigantic child's spinning top. As it danced everything it bumped into or moved over disintegrated.

The operators had foolishly pushed the failed generator to it's absolute maximum one too many times and all hell broke loose.

This is one possible reason China might be reducing stress on it's power machinery at three gorges dam. To avoid something like this.
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Great post.

I’ve been in a few hydro dams, very impressive examples of civil engineering.

Hydro dams are increasingly in the headlines in recent years, due to their under appreciated importance.

Iraq’s Haditha Dam seizure from Saddam Hussein’s forces to prevent its demolition and flooding...and eventual recommissioning.

Ukraine’s Dnieper Dam kinetic cyber attack by Russia in 2015-2017

Afghanistan’s Kajaki Dam 10 year battle against the Taliban to deliver a turbine and commission the dam to connect it to the national power grid

Ethiopia’s Grand Ethiopia Renaissance Dam that is majority complete and currently having its reservoir filled violently opposed by Egypt(with military units specifically trained to seize upriver infrastructure recently trained by US/UK forces)

Much as we under appreciate the importance of protecting against pandemic, the same can be said with national infrastructure of international importance.

[touchring]

Re: Big Trouble in Little China

https://www.google.com/maps/search/t.../data=!3m1!1e3

This looks dramatically better than the photos in Mike's original post. I'll assume the direct google map image at the link here is a truthful image, the after image in the article is false, and the dam has not moved much.

There's a lot of fake satellite photos showing the dam highly distorted which I read is impossible because concrete would have disintegrated if they could be seen distorted that way visually. I don't believe the dam would collapse just because of one flood, but if this flood repeats every year and along with some future seismic event, the lifespan of the dam could be reduced to maybe only decades instead of 100 years originally planned.

Read this from the state media. This was 30 June before the flood became really serious in mid-July.

. The move aimed at reducing the reservoir's water level from 147.51 meters days ago down to a safe level of 145 meters, following days of heavy rain.

[thriftyandboringinohio]

Re: Big Trouble in Little China

In 2009 a Russian hydro dam had a catastrophic failure of the power machinery. The dam structure as a whole stayed intact and held back the river. The power plant is just finishing repairs now, a decade later.

Here's some photos






If you haven't spent time in big hydro dams you might not appreciate the enormous scale of this structure.
In the rubble on the right, look at those yellow cranes. Those are big hundred ton cranes.
In the "before" picture, notice the circles on the floor. Those are the top covers for the round generators; the water turbines are a few stories below, down in the water.

Here's a shot of a generator rotor after the event. It's one of the circles on the floor. Notice the people standing on the rotor to get a sense of scale.
There is not much empty space or air in such a rotor. You can think of it as a solid chunk of copper and steel.
Hidden under it is the main drive shaft going down to the turbine. It's a solid steel shaft about 3 feet in diameter and maybe 30 feet long. Close under this rotor is a shaft coupling to disconnect it. The coupling is pretty close to the generator rotor, so the rotor stub shaft to the coupler might be eight or ten feet long.



Hydro generators turn at low speeds, this one turns at about 140 RPM. I would expect this rotor to weigh about 250 tons; that's 40 fully loaded semi trucks.

A rotor like this was the problem. I don't think it was this particular rotor because it looks like this one's still inside the ruins of it's stator.
But one of these broke free at speed. It bashed through the structure around it, and went dancing across the generator deck on it's stub shaft like some gigantic child's spinning top. As it danced everything it bumped into or moved over disintegrated.

The operators had foolishly pushed the failed generator to it's absolute maximum one too many times and all hell broke loose.

This is one possible reason China might be reducing stress on it's power machinery at three gorges dam. To avoid something like this.
.
.
.
.

[thriftyandboringinohio]

Re: Big Trouble in Little China

... The controversy was the dam opened the flood gates in late June even when the water levels were much lower than a couple years before, leading to speculation that the dam was structurally weaker than it was previously...

That is indeed pretty strong evidence the dam has serious problems. This dam is a major hydro power plant. Lowering the water level (the hydraulic "head" for the turbines) dramatically reduces power output. Head level for the turbines is fundamental to the design of the whole gigantic system. The authorities would not lower it without a lot of meetings and some pretty serious concerns.

Those concerns might not be about the dam collapsing. It might be problems with the turbine runners, or wicket gates, or penstock, or tailrace... Some of the power machinery may be faulty and need reduced stress.

I spent all of 5 minutes googling around this and didn't find any formal warnings from engineering societies or government bodies, but then this is China. Most of the chatter seems to be exactly as Mike originally posted, those before and after Google Earth photos. China says the photos are doctored and false. Here's what Google maps shows now

https://www.google.com/maps/search/t.../data=!3m1!1e3

This looks dramatically better than the photos in Mike's original post. I'll assume the direct google map image at the link here is a truthful image, the after image in the article is false, and the dam has not moved much.

But if they've lowered the pool level and kept it down, something is seriously wrong somewhere.

[thriftyandboringinohio]

Re: Big Trouble in Little China

Thank you, but that is not what I wished to see; what I need, please, is a credible report showing the suspected damage to the dam itself; actual images of the shift of the line of the dam.

Dams are more complex than just a log thrown across a stream. There are a few different construction types, and each has more than one mode of failure.
Some of the failure modes are not visible in aerial photography. Some failures are structural (cracks and breaks and movement) and some are hydraulic (seeps and boils and undermining).

[Chris Coles]

Re: Big Trouble in Little China

" ... following days of heavy rain."

I'm just shaking my head. Here the BIG NEWS is the 0.07" of rain we got today at the airport. Our first measurable rain in 103 days. YAY!!!

The world's a funny place.

By chance, this very morning, a friend in North Island New Zealand reports that a friend of his, further north, has just reported that they had 250mm, just under 10 inches of rain.

[shiny!]

Re: Big Trouble in Little China

" ... following days of heavy rain."

I'm just shaking my head. Here the BIG NEWS is the 0.07" of rain we got today at the airport. Our first measurable rain in 103 days. YAY!!!

The world's a funny place.

[Chris Coles]

Re: Big Trouble in Little China

Here's a Chinese state media report on 30 June before the floods became serious.

https://news.cgtn.com/news/2020-06-3...UFG/index.html

Thank you, but that is not what I wished to see; what I need, please, is a credible report showing the suspected damage to the dam itself; actual images of the shift of the line of the dam.

[touchring]

Re: Big Trouble in Little China

Thanks, can you provide a link to what you consider to be a credible report please.

Here's a Chinese state media report on 30 June before the floods became serious.

https://news.cgtn.com/news/2020-06-3...UFG/index.html

The Three Gorges Dam located in central China's Yichang City discharged water on Monday. The move aimed at reducing the reservoir's water level from 147.51 meters days ago down to a safe level of 145 meters, following days of heavy rain.

[Chris Coles]

Re: Big Trouble in Little China

It's all over Youtube, lots of talk about it. Just like covid, there's no "report" of where it came from and what happened. All are speculation.

Thanks, can you provide a link to what you consider to be a credible report please.

[touchring]

Re: Big Trouble in Little China

That is something I did not know about, which begs the question, is there a more detailed report currently available to show us what has recently occurred at the dam? Without such we are all in the dark.

It's all over Youtube, lots of talk about it. Just like covid, there's no "report" of where it came from and what happened. All are speculation.

[Chris Coles]

Re: Big Trouble in Little China

The purpose of a dam to is hold back water until it overflows. The controversy was the dam opened the flood gates in late June even when the water levels were much lower than a couple years before, leading to speculation that the dam was structurally weaker than it was previously.

For me, the smoking gun is the unusually strong official denials even when main stream media haven't really taken up the issue.

That is something I did not know about, which begs the question, is there a more detailed report currently available to show us what has recently occurred at the dam? Without such we are all in the dark.