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Thread: Retaining wall delima

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    Ksnewman's Avatar
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    Retaining wall delima

    I am fairly new to site and definitely new to pool ownership so I have been scouring site for months and have found that there is a wealth of knowledge represented; therefore, I come humbly seeking advice.
    We are in process of building Versa-lock wall which will be abt 10' at tallest point and 130 ft long with avg depth of 6'. We have had it engineered and will, of course, be using geogrid for reinforcement. Bacically we are creating back yard which pool can be built. PB would like compacted crusher run under pool but we do have to back fill the 8' or so from wall with something. Engineer recommended #57 stone which takes very little compaction but does cost more per ton than crusher run. Crusher run is less but what I don't know is what all is involved in compacting. Obviously it will increase cost but not sure if I would be just as well off to use the 57's.

    I appreciate any thoughts or opinions. At this point, I feel we are building the Great Wall of China! DH has put me in charge of contracting which I am not a novice; however, in the arena of pools and retaining walls....So much to learn.

    I will post photos of progress but change topic to "have we lost our minds!"
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    Mod Squad JohnT's Avatar
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    Re: Retaining wall delima

    Welcome to TFP!

    Disclaimer: I'm an engineer, but not a civil engineer. I only mess around building my own stuff on the farm.

    Keep in mind that stone terms are used differently in different areas. In the NE, granite is the primary stone. In some areas, river gravel is heavily used. Both behave differently than limestone in uncleaned mixes so when researching, consider the source of information and talk to the engineer if you can.

    I think any material you fill with needs compacting. 57s are only about 90% compacted out of the truck, where I think crusher run is about 80%. 57s can settle about 1" per foot, while crusher run can settle as much as an inch per 5" depth. Crusher run can vary quite a bit in size and therefore performance. Typically you will see about 20% more cost for the 57s on a per ton or volume basis, but some of that may be made up in the compaction of the material being different. You'll put ~10% less 57s down to fill the same volume.

    Since this is the foundation for your pool, I'd use the 57s AND compact. Compacting will consist of going over the gravel in layers with either a ride on rolling compactor which is the best if your contractor has access to one, or with a walk-behind plate compactor. The standard for layers depends on the method of compacting. I go with 6", but that's doing work for myself.
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    Re: Retaining wall delima

    Welcome to the forum. Is there a reason to doubt the engineer you have hired to consult? I would sure stay with his advice unless you have some reason to change.

    For what it's worth, I would use #57 stone as partial backfill for the wall and I like the idea of crusher run under the pool although most PB's use nothing.
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    Re: Retaining wall delima

    I'll just chime in to agree that you should follow the engineers recommendation. You can certainly ask them if you could use crusher run as the pool base and that'll probably be fine. The key is the compaction.
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    Re: Retaining wall delima

    As a builder we use only clean rock. For vinyl with a polymer wall we use only 1" clean limestone, no compaction around the wall as it can push the wall inwards. Around our one piece fiberglass we use 3/8" clean limestone as per manufacturer specs. By clean it has been through a wash plant to remove dust. Several years ago we built a pool in a similar situation as yours but to save money the homeowner decided to fill with waste and didn't compact it. The pool has settled about 3" so far. Do discuss with your local engineer and take their recommendations as being the best ideas for your situation. The forum is a good thing, but your local engineer knows more about your exact situation.
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    Re: Retaining wall delima

    Quote Originally Posted by duraleigh
    Welcome to the forum. Is there a reason to doubt the engineer you have hired to consult? I would sure stay with his advice unless you have some reason to change.

    For what it's worth, I would use #57 stone as partial backfill for the wall and I like the idea of crusher run under the pool although most PB's use nothing.
    The engineer said I could use either. I am trying to get a more definitive answer as to what is going to be the most cost effective at the end of the day. I have more than 250 CY of material to bring in. That's alot of $$$ so just wanting to be sure that I make the best of use of my $$$! Thanks!
    18x36 kidney 20,000 gallons IG vinyl. Pentair Easy Touch 8 w/IntelliChlor IC40. Triton II TR100. Pentair Intellifllo Variable Speed. Waterfall/Jump Rock. 2 Pentair Intellibrite lights. TF-100 Test Kit. And a very happy husband who gets to play in the pool without having to take care of it.

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    Re: Retaining wall delima

    1) Nothing is "self-compacting" or more to the point, everything is self-compacting to a point, but all will compact more once overburden is placed on it.

    2) #57 is clean stone, crusher run has fines in it. The crusher run needs more compacting because the fines need to "sift" their way into the small void spaces between the larger aggregate. With no fines in it #357 does not need as much compacting. However, what are you going to put on top of your #57? If you put something with fines in it (sand, loan, etc) that eventually find its way down into the #57

    3) There are a number of schools of though about what to put behind a retaining wall. Clean stone, such as #57 does not need as much compaction, so there is less of a chance of the retaining wall shifting when you compact behind it. The open structure of the clean stone also allows water to drain, reducing the hydraulic head that is behind your retaining wall. Crusher run compacts well, does not "shift" underfoot, and if you build on top of it, does not require as spread a footing.

    It's is really a decision that is up to you. If you have provided for correct drainage (Crushed stone / geotextile under the wall and along the back, weeping tile, and proper slope/grading) then crusher run should not pose a problem.

    Technicaly, since this is going to be a lawn area (I presume) you can "get away" with less stringent compaction methods as there is less loading.

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    Re: Retaining wall delima

    Yes, I would agree there, for me the most important thing would be having allowed adequate drainage for water behind the wall. If thats been neglected I'd definitely go for the larger stone for bulk followed by grade. One thing I've found with sandstone based crusher run, is that it can compact a little too hard, therefore preventing drainage..........water....always a nightmare!!
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    Re: Retaining wall delima

    I have over 1000 sq feet of vers loc in my yard. Had to build a 6 foot wall behind the pool, and an 8 footer on the side to level the yard.

    I back filled it with 3 feet of 3/4" stone (basically #57) and topped it off with processed gravel (thats basically what crusher run is called in New England, although the material is sieved a bit more). We compacted the geogrid in the processed material with a heavy plate compacter. The ppoblem with running the stone all the way up to the top is compaction. It wont compact the geogrid as well as processed material. The idea is to back fill with the stone for water drainage with a weeping system buried in the stone, the the processed material holds the geogrid. Be sure they cover the back of the wall with fabric so it wont weep. Vers loc is good stuff, it just needs to be installed properly. Sounds like the gys you have know what they are doing.
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    Re: Retaining wall delima

    I think maybe there is some confusion on the actual construction of this pool and wall. Maybe the OP can clarify this sentence:

    "PB would like compacted crusher run under pool but we do have to back fill the 8' or so from wall with something."

    Is the pool below the wall or above it relative to the original grade? I assumed above, since I could see no other reason for putting crusher run under the pool.
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    Re: Retaining wall delima

    I'm assuming this is an overdug liner pool with walls and he needs a retaining wall to level the yard. The wall would create a level back yard with the top of the pool being very near flush with the top of the wall. The builder wants to put some crusher run in the bottom of the pool i assume to give it some support. The way we did ours was to put in the weeping tiles behind the wall, then partially backfill the wall with stone. Once that was done, the pool itself was dug, the pool walls set, then the retaining wall was backfilled with the processed material in layers as the geogrid was laid over and compacted. We had 3 layers of grid spaced about 2 feet apart.
    Below are a few picutres of the process. Is this close to what you are doing?









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    Re: Retaining wall delima

    Quote Originally Posted by bk406
    I'm assuming this is an overdug liner pool with walls and he needs a retaining wall to level the yard. The wall would create a level back yard with the top of the pool being very near flush with the top of the wall. The builder wants to put some crusher run in the bottom of the pool i assume to give it some support. The way we did ours was to put in the weeping tiles behind the wall, then partially backfill the wall with stone. Once that was done, the pool itself was dug, the pool walls set, then the retaining wall was backfilled with the processed material in layers as the geogrid was laid over and compacted. We had 3 layers of grid spaced about 2 feet apart.
    Below are a few picutres of the process. Is this close to what you are doing?









    18x36 kidney 20,000 gallons IG vinyl. Pentair Easy Touch 8 w/IntelliChlor IC40. Triton II TR100. Pentair Intellifllo Variable Speed. Waterfall/Jump Rock. 2 Pentair Intellibrite lights. TF-100 Test Kit. And a very happy husband who gets to play in the pool without having to take care of it.

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    Ksnewman's Avatar
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    Re: Retaining wall delima

    Quote Originally Posted by JohnT
    I think maybe there is some confusion on the actual construction of this pool and wall. Maybe the OP can clarify this sentence:

    "PB would like compacted crusher run under pool but we do have to back fill the 8' or so from wall with something."

    Is the pool below the wall or above it relative to the original grade? I assumed above, since I could see no other reason for putting crusher run under the pool.
    Sorry, the pool is actually about 1' above wall grade. The question really was what to back fill the wall with. We will use drainage aggregage behind wall for 1' or so and the rest of the fill will be crusher run - compacted. That seems to be the consensus.
    18x36 kidney 20,000 gallons IG vinyl. Pentair Easy Touch 8 w/IntelliChlor IC40. Triton II TR100. Pentair Intellifllo Variable Speed. Waterfall/Jump Rock. 2 Pentair Intellibrite lights. TF-100 Test Kit. And a very happy husband who gets to play in the pool without having to take care of it.

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    Re: Retaining wall delima

    Here are a few photos of the "great chasm" as I fondly refer to it. It seems like an impossible task, but I know it won't settle. Everything will be sitting on solid rock.
    Attached Images Attached Images
    18x36 kidney 20,000 gallons IG vinyl. Pentair Easy Touch 8 w/IntelliChlor IC40. Triton II TR100. Pentair Intellifllo Variable Speed. Waterfall/Jump Rock. 2 Pentair Intellibrite lights. TF-100 Test Kit. And a very happy husband who gets to play in the pool without having to take care of it.

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    Ksnewman's Avatar
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    Re: Retaining wall delima

    Quote Originally Posted by bk406
    I have over 1000 sq feet of vers loc in my yard. Had to build a 6 foot wall behind the pool, and an 8 footer on the side to level the yard.

    I back filled it with 3 feet of 3/4" stone (basically #57) and topped it off with processed gravel (thats basically what crusher run is called in New England, although the material is sieved a bit more). We compacted the geogrid in the processed material with a heavy plate compacter. The ppoblem with running the stone all the way up to the top is compaction. It wont compact the geogrid as well as processed material. The idea is to back fill with the stone for water drainage with a weeping system buried in the stone, the the processed material holds the geogrid. Be sure they cover the back of the wall with fabric so it wont weep. Vers loc is good stuff, it just needs to be installed properly. Sounds like the gys you have know what they are doing.
    Would love to see pics. We are using Versa-lock. Engineer didn't mention covering back of wall. I will look into that. Thanks!
    18x36 kidney 20,000 gallons IG vinyl. Pentair Easy Touch 8 w/IntelliChlor IC40. Triton II TR100. Pentair Intellifllo Variable Speed. Waterfall/Jump Rock. 2 Pentair Intellibrite lights. TF-100 Test Kit. And a very happy husband who gets to play in the pool without having to take care of it.

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    Re: Retaining wall delima

    phonedave
    Thanks for the info. Definitelly Geogrid & drain pipe at base. We will compact in 6" lifts. I may learn to use a compactor. I may be a female but I love construction!
    18x36 kidney 20,000 gallons IG vinyl. Pentair Easy Touch 8 w/IntelliChlor IC40. Triton II TR100. Pentair Intellifllo Variable Speed. Waterfall/Jump Rock. 2 Pentair Intellibrite lights. TF-100 Test Kit. And a very happy husband who gets to play in the pool without having to take care of it.

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    Re: Retaining wall delima

    I used 57 stone behind my wall. I've got 2 - 4' walls and did it over 2 years ago. No sign of any movement and I've got a pretty big hill/driveway behind the wall. I always thought you should always use 57 stone for good drainage behind the wall. I've got perforated pipe running the entire wall for drainage and it appears to work very well.
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    Re: Retaining wall delima

    Quote Originally Posted by XsAllOverIt
    I used 57 stone behind my wall. I've got 2 - 4' walls and did it over 2 years ago. No sign of any movement and I've got a pretty big hill/driveway behind the wall. I always thought you should always use 57 stone for good drainage behind the wall. I've got perforated pipe running the entire wall for drainage and it appears to work very well.
    Thanks for the info. We will be going with a combination of 57 stone behind wall and the rest with crusher run. We have a huge hole to fill. It looks like crusher run gives best compaction with geogrid and 57's immediately behind wall for drainage.
    18x36 kidney 20,000 gallons IG vinyl. Pentair Easy Touch 8 w/IntelliChlor IC40. Triton II TR100. Pentair Intellifllo Variable Speed. Waterfall/Jump Rock. 2 Pentair Intellibrite lights. TF-100 Test Kit. And a very happy husband who gets to play in the pool without having to take care of it.

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    Re: Retaining wall delima

    Quote Originally Posted by Ksnewman
    It looks like crusher run gives best compaction with geogrid and 57's immediately behind wall for drainage.
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