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Thread: Pond Design & Construction post Japan earthquake

  1. #1
    Oyagoi mrbradleybradley's Avatar
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    Pond Design & Construction post Japan earthquake

    Hi

    I was wondering if those who have been in Japan since the earthquake damaged ponds if/how pond design may have changed to make them more quake proof.

    Thanks

    BB

    ps. I promise I really can spell "construction"

  2. #2
    Jumbo jnorth's Avatar
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    Quote Originally Posted by mrbradleybradley View Post

    ps. I promise I really can spell "construction"
    Fixed that for you .
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  3. #3
    Oyagoi mrbradleybradley's Avatar
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    I am told that bottom drains are out and side drains are in. Apparently some ponds post earthquake were inspected and believed to have survived the quake. Then the owner came back later to find the water had leaked through a damaged bottom drain or pipework underneath the pond. Supposedly the side drain is to give better inspection of the drain and pipework in future.

  4. #4
    Daihonmei MikeM's Avatar
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    Interesting. Perhaps that explains the new Ogata pond design with a raised center so waste goes to the sides for capture. They borrowed vortex settlement chambers from Western practice, but I could not understand why they went to so much trouble not to have central bottom drains.

  5. #5
    Oyagoi koiczar's Avatar
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    Hadn't seen any of that in recent trips. Maybe I wasn't looking hard enough but I saw some brand new green houses, built within the last 1-2 years. All still had central drains with covers or the simple steel grate over them, just like PRE earthquake period. I don't get down to Hiroshima at all but where most of the damage was done in Yamakoshi, it's design/business as usual. Some ponds were seriously upheaved from the ground - remember seeing one that was about 6-9" higher at one end. It looked funny due to the water level looking cockeyed!LOL But, the cracks in the pond were simply filled in with something and then repainted.

    I can see where a side drain might make sense from an inspection ease of repair point of view. I wonder why it's not done more?

    Mike

  6. #6
    Jumbo
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    I'm assuming that Bradley's post relates to mud ponds, not concrete ponds, perhaps he can confirm?

    I've seen mud ponds with bottom pipes, out the side pipes and over the side pipes.

    On many occasions I've stood on the sides of mud ponds with the obvious reality that, should a major earthquake occur, the land beneath me could quite easily collapse beneath my feet.

    I don't think it really matters where the plastic pipe passes through the wall of a pond, if the ground shakes violently a piece of 6" plastic pipe creates a natural weakness, as any gap opens between the pipe and mud water will simply force it's way through, the force of water likely to break the bank.
    Mark Gardner

  7. #7
    Administrator Brian's Avatar
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    Most of the indoor concrete ponds that I've seen here are constructed from steel-reinforced poured concrete which are quite strong in themselves. If the integrity of the ground that the pond sits on is compromised then even a strong pond like this is likely to crack.

    For small to medium-sized tremors though, this construction is quite solid. Trying to protect a mudpond against fissures seems prohibitively expensive though, especially when built on the hillside.
    Brian Sousa
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  8. #8
    Jumbo jnorth's Avatar
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    Quote Originally Posted by koiczar View Post
    I can see where a side drain might make sense from an inspection ease of repair point of view. I wonder why it's not done more?

    Mike
    I was thinking the same thing. With a side drain if there is ever an issue you could out around the wall of the pond and make repairs withpout having to break up the floor of the concrete pond. I guess the real question is: How effective is a side drain and does ease/cost of repairing a side drain outweigh the assumed greater effectiveness of a regular bottom drain?
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  9. #9
    Oyagoi mrbradleybradley's Avatar
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    Hi Mark

    I am told that the design relates to concrete ponds.

    BB

  10. #10
    Oyagoi koiczar's Avatar
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    I figured they were talking about concrete ponds. One thing for certain, when you consider the size of a standard greenhouse with 6-8 ponds and the amount of concrete that is placed in them, usually above ground, I sure as heck wouldn't want to try to repair a drain pipe that was underneath it all - especially POST EARTHQUAKE. Had my share of crawling around in the roof crawl space in a building out at Stanford after the '89 Loma Prieta quake - DON'T WANT TO BE DOING ANYTHING LIKE THAT AGAIN REAL SOON!! It's like waiting for the other shoe to drop - only the shoe is a sledge hammer!LOL

    I can certainly understand their interest in this idea. If the pipe is embedded in the concrete wall rather than through the floor into the ground and cannot shift between ground and concrete, there is much less stress to cause a pipe to crack/break. It actually might save a few greenhouses in the offing!

    Mike

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