Ground settling under pool deck concrete

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Old 03-10-16, 01:47 PM
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Ground settling under pool deck concrete

About 6 months ago I had an inground pool put in, with stamped concrete around it. Since then, the dirt under the concrete has settled and there is about a 6" gap between the concrete and dirt just about all the way around the pool. They did use sonotubes, so the concrete has not cracked or sunk one bit. Im just worried that over time it will. Is this typical? Is there anything I need to do? In multiple spots i can look underneat the 3 ft wide concrete and see the side of the pool. Ill see if i can figure out how to upload photos of it. Thanks in advance!
 
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Old 03-10-16, 01:56 PM
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Since you paid to have this done, I would call the contractor.
 
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Old 03-10-16, 02:13 PM
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I made the mistake of trying to save money, and found someone on craigslist that does it. He has pretty much avoided me ever since the job was completed. In all fairness though, he was about half the price of the other quotes i received. Im actually happy with how it turned out except for this issue. I would rather just try and deal with it myself.
 
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Old 03-10-16, 02:21 PM
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How about some pictures of what you're seeing?
 
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Old 03-10-16, 02:32 PM
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Everytime i try to upload a picture (on my iphone), it says upload failed :-/
 
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Old 03-10-16, 02:34 PM
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May have to resize - pictures from phones are often too big.
 
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Old 03-10-16, 03:28 PM
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Name:  image.jpg
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Here, lets see if this works! I cropped the picture to make it smaller.
 
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Old 03-10-16, 03:34 PM
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Dont know why the first pic came out so weird. Here, i tried another.
 
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Old 03-10-16, 07:39 PM
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This is all settling and not erosion?

Was no compacting done first?
 
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Old 03-10-16, 08:37 PM
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Most the work was done when i was not home, so i am not sure if any compacting was done. (Altho im willing to guess it wasnt)
 
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Old 03-11-16, 05:46 PM
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I'm really surprised that deck hasn't cracked yet. Obviously the contractor knew that settlement of the soil is going to be a problem in this way put in the sonotubes. Doing it really isn't a normal practice under sidewalks and such. How close together are the tubes?

About the only way you're going to fill in that void is to have grout injected into it. Doing that takes specialized equipment to ensure that the grout goes all the way back in to completely fill the void. If you don't do something that sidewalk is certainly going to crack relatively soon.
 
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Old 03-11-16, 06:21 PM
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I have to agree.... I'm baffled with the use of sonotubes there. The look of the deck is nice but you've got a problem there and not an easy repair.

In order to inject concrete under the deck there would need to be forms put on the visible side to contain the concrete but that will bring up a new problem as there is no proper footing under the rest of the deck and it will expand and contract differently from where the tubes are risking cracking. I don't see an inexpensive repair remedy.
 
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Old 03-11-16, 08:36 PM
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I thought it was normal practice to use sonotubes around an inground pool where the dirt has recently been backfilled. The pool company is actually who put in the sonotubes, it was a separate contractor who did the actual concrete work. Here is a pic of the pool before it was backfilled where you can see the tubes.

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Old 03-11-16, 09:20 PM
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What about digging out around the sides some, and getting real wet concrete underneat of it? Even if it doesnt fill the void 100%, hopefully it would be enough to prevent cracking.
 
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Old 03-11-16, 09:21 PM
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Ahhh..... good picture. I read inground pool and thought concrete/Gunite.

That certainly changes things as you can't just pumping concrete in there without buckling the sides of the pool. Perhaps someone has a an idea they could share with us.
 
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Old 03-13-16, 12:34 PM
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Thanks for the picture, that gets us a lot more information what you are seeing and what was done originally. Both tubes look like they are actually PVC pipe, is that what they are? They really are spaced close enough together to provide a lot of support for the sidewalk considering it's so thin.

Just putting wet concrete back in there isn't going to help much, especially if the ground is still settling which it probably is. Even if you pumped grout into the void, which I think could be done if the pool is full to provide resistance, the ground would still continue to settle and probably cause future problems.

I'm not sure there's a good solution to your problem. The best solution would be to remove the sidewalk and compact the soils correctly that even would be difficult because of the type of pool you have. Certainly need to do something because that sidewalk is definitely going to fail sooner rather than later.

Just wondering what kind of soils were used for the fill? That will easily make a big difference about how much they will end up settling.
 
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Old 03-14-16, 05:57 AM
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The soil used to backfill was the same soil they dug out to put the pool in. Yes, they are PVC tubes that go down into the concrete at the base of the pool. The tubes were then filled with concrete to provide support for the sidewalk. I ended up getting in touch with the contractor that did the work. He is going to come out and see if theres anything he can do. He said you cant compact the soil around a pool like mine because you could damage the water lines that go around the outside of the pool. Which actually does make sense, but just seems like there should certainly be something you could do to prevent this from happening. I have a hard time believing it looks like this under all inground pool concrete!
 
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Old 03-14-16, 09:25 AM
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I can't believe anyone said the PVC filled pipe was a support for a cement walk. My guess is they are supports for a wooden deck frame, much like the lolly columns used to support the beams in a basement. Even then I would be wary because the PVC filled pipe will crack with little side motion. When, not if, that cement walk breaks. good chance it could damage the wall of the pool. I would have a contractor remove it ASAP.
 
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Old 03-18-16, 08:31 PM
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So what's the problem? You're happy with your CL contractor, and his flimsy excuse as to why he doesn't compact the ground under his flatwork. There's no easy or permanent fix to the mess he left you, but just remember that you got what you paid for.
 
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Old 05-23-16, 08:11 PM
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If the OP hasn't found a solution for his settling problem, I'd suggest the following:

1. Build a perimeter form around the entire affected area, about a foot away from the existing concrete and about a foot above it.

2. Build a wall form on top of the existing deck at its edge, same height as the outside form. Make sure the bottom of the wall form is tight against the deck concrete.

3. Pour self-consolidating concrete into the formed area. With enough ambitious guys on shovels, and judicious use of a spud vibrator or two, the fluid concrete can be worked under the existing deck to fill the voids. I've seen SCC moved close to 15' horizontally just using the above method.

4. When no further settlement of concrete between the wall form and outside form is visible, call it good, and then have the grunts shovel all of the excess (waste) concrete out from between the forms, and finish what's left appropriately. A nice contrasting texture, or even exposed aggregate, would look decent.
 
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