The geological issues of the Fukushima Daiichi

~kujala~

The problem is we don't know if it's a real floating box design. I have tried to find out information about Fukushima I foundation type but hasn't been able to find it. Anybody else luckier?
Just because there is a thick bottom concrete doesn't make it a floating box. If it's a floating box design then all of the bottom concrete is a supporting structure. To build it like this is expensive.
If it's not a floating box then there are weaker parts and stronger parts in the bottom concrete.
Another interesting thing is do they have a base isolation system or some other seismic vibration control system.
I guess the simplest/cheapest design would be this: there are footings that support the weight of the building and then there are beams to transfer weight from one footing to another if there happened to be a landslide underneath one footing.
These are interesting things to study on their own.

I think we have to separate two things here.
The first thing is a crack which is directly created by a fault line. I have an impression that these cracks rarely cut through hard rocks in Fukushima area although now this has happened:
The second thing is the shaking of the ground itself. When the ground is shaking the weaker soil on top of the hard rock could (or could not) amplify the shaking.
How much this has happened in the Fukushima area is again an interesting thing itself.

I agree. And the radioactive levels of seawater have been decreasing so we know there should be no big leaks from polluted groundwater into the sea. This would suggest that deeper groundwater is perhaps not that polluted at all.

As far as I see it, there are larger issues concerned.

At one point there was a news report where TEPCO said it cannot deny the possibility that in the number #3 reactor some major damage could have been done by the earthquake itself (I think it was a piping system).

It will take many years until they will finally conclude did the earthquake itself cause any major problem. And who is going to study it? TEPCO itself or some independent research team? (I hope the latter and I hope also not just an IAEA team.)

If at the end they would conclude that the earthquake itself actually did cause some major damage they would also start to find reasons behind it.

One thing is of course that ground acceleration numbers were above design parameters. But at this point they could also question if the whole plant has been built in a proper place / in a proper manner (soil amplification & foundation type etc).

The soil amplification studying as a branch of science is quite young, AFAIK, at least when it concerns the actual maps over different areas. Perhaps the theories are older. For instance: do they have soil amplification maps all over Japan? When I studied a little bit soil amplification maps from the U.S. I noticed some of them were made only quite recently. Like this one was presented in 2002, perhaps made a couple of years earlier:
http://gsa.confex.com/gsa/2002NC/fin...ract_31500.htm

So even if we don't know how is it going to proceed it is still an interesting thing to study. How well are the soil amplification aspects understood all over the world? What kind of foundation types are they using when they are not building on a top of granite/other hard rock? Should a proper soil amplification study be required in the future when building in seismic areas? How about existing NPP:s, should we force them to make soil amplification studies if none exists for that area?

These are interesting questions and I think one can study it a little further without speculating. Like: What kind of foundation type do they really have in Fukushima? Do they have soil amplification maps all over Japan?

~kujala~

Discussion about the definition of 'bedrock' from another thread:

http://www.physicsforums.com/showthread.php?t=499725

This discussion could perhaps be directed here as it contains same issues that has also been discussed in the main thread.

One thing to note:
Earlier I proposed that S-wave velocity could be used as some kind of indicator how strong the rock is. Well, this perhaps applies to some extent but to make a precise analysis more information is needed.

Edit: Could somebody (native-English) propose better tags?
Now I have: # foundation # geology # groundwater # rock # soil

joewein

I came across the following in an article in the German daily "Die Welt" published on March 15 about whether or not contamination of the water table was likely, which talks about the local type of rock:

English translation by me:
German original:
The article mentions that around the power plant several metres of sandstone sit on top of the claystone, but it was removed where the foundations were built, for example at unit 3 where these foundations reach 16 metres deep.

It also mentions that the base of the foundations is a 4 metre thick slab of reinforced concrete.

You can use Google translate or Google Chrome to read a rough translation of the complete article into the language of your choice.

~kujala~

Recently there has been a couple of great posts concerning groundwater contamination / geological structure of the Fukushima plant. I am linking them here so that they can be easily found later:

First one was by tonio who says he is a geologist, specialized in soil and groundwater contamination:

http://www.physicsforums.com/showpos...postcount=9285

The second one was by Azby who was able to get some information from a Japanese specialist, a professor of geology:

http://www.physicsforums.com/showpos...postcount=9753

My question for tonio: In one paper TEPCO said they are going to empty the contaminated sub-drain pits of the unit #1 - #4 at some point. How is it controlled that these sub-drain pits won't overflow? Is there some kind of automatic measurement of the water level in the sub-drain pits or are they controlled manually?

I have not noticed TEPCO saying that they have emptied the unit #1 - #4 pits. For units #5 - #6 they did it a long time ago. There might be more groundwater near #5 - #6 than #1 - #4.

http://varasto.kerrostalo.huone.net/salaojat_1.png

ribeditaa

What is the best university to study geology in Australia? I have applied for a BAs(geology) at UWA and don't know whether I have chosen the right uni. Are there any better ones to go to? Also, what are the chances of getting a job after completing the BAs in geology in the resource sector for Australia, I thought it looks good so thats why I'm changing my career. I'm 27 now and thought I still have time :) let me know your thoughts. Thanks!