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Old 10-26-2012, 12:03 PM   #1
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Sand Fill For Swimming Pool


We are considering using the area now occupied by a 16' x 32' in-ground
gunite swimming pool for two purposes. One end would have an enclosed shallow exercise pool, probably 16' long x 12' wide and 6' deep. The building over the new pool would be insulated and have large sliding glass doors so that the pool would have an open feel in good weather (about 4 months a year).

The other area would be a patio and/or garden area.

I've read of several methods to remove a swimming pool. One requires that all the concrete be broken and removed. Then, if the area is to be built upon, select fill is to be compacted in layers. Another method demolishes the upper wall sections and pushes them into the pool bottom.
Then fill dirt and rubble is pushed in. The area filled in this way will probably
subside irregularly over the next years.

My idea is to simply fill the pool with very wet sand. A drain at the bottom of the pool with filter fabric would allow the water used to consolidate the sand to escape.

When the sand reaches the level of the bottom of the new pool, a fiberglass shell would be lowered into the hole and more sand would be added and consolidated with lots of water. The building footings and slab would be poured on consolidated sand also.

This method saves the cost of demolishing and removing the concrete shell. It also eliminates the need for compacting equipment.

Seems too simple. Now why won't it work?

PS: Just got a ballpark estimate for delivering the sand (120 cubic yards): $2600. The sand would still need to be moved from the driveway to the pool area. Perhaps a Bobcat or skid loader would do the actual fill.

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Last edited by Thumbhammer; 10-26-2012 at 12:22 PM. Reason: Additional Info
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Old 10-26-2012, 03:03 PM   #2
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Sand Fill For Swimming Pool


What kind of sand would you use for this project???

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Old 10-26-2012, 03:44 PM   #3
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What kind of sand would you use for this project???
I assumed that "fill sand" was just sand. However, I read that it can contain silt and clay. The processed varieties are probably much more expensive.
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Old 10-26-2012, 05:03 PM   #4
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Sand Fill For Swimming Pool


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Originally Posted by Thumbhammer View Post
I assumed that "fill sand" was just sand. However, I read that it can contain silt and clay. The processed varieties are probably much more expensive.



In that case it would plug up your filter cloth,and pose a drainage problem,at $21.00 a yard i would think you would get something a little better suited to your project

Have you seen this sand,and if so is it a coarse or fine variety???
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Old 10-26-2012, 05:15 PM   #5
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Sand Fill For Swimming Pool


The reason your method would not work is that water does not act to consolidate sand. The placement method you describe is similar to hydraulic fill, which is commonly done using a high pressure slurry of water and sand, shot out of a hose, which fills the hole. This method has also been used to construct sand core dams, occasionally with tragic results, since the wet sand DOES NOT consolidate even when the water is drained, leaving it in a loose, weak condition, which can lead to unexpected future settlement.

If the fill does not need to be consolidated, because there is no construction planned above it, or the construction above it is lightweight or resistant to settlement, the method can and is used as a low cost alternative to conventional placement (with compaction) of structural fill.
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Old 10-26-2012, 05:35 PM   #6
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Sand Fill For Swimming Pool


Daniel is right about the pumped or dredge fill that is placed. When it drains, there is some minor compaction that can be too low to put a structure on and looses strength when there is water available, such when the ground water comes up or the drain plugs. It would not be good to put a structure on it (grade beams, footings) are try to depend on it to support a small pool that could settle or float.

The best way probably would be to crack up the pool floor and walls, put some larger pieces in the pool area (not trying to fill it), "choke" the voids with a controlled material to eliminate voids and then to put in a compacted (vibratory compactor) material in lifts to make it at least as strong as the undisturbed natural soil.

I have seen the coarse(very large) rock from blasting dumped,
"choked" with sand and fine rock and then covered this area with a good depth of compacted layers of road base to make a road for 100,000# mine trucks in a 100' deep fill area.

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Old 10-27-2012, 11:20 AM   #7
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Originally Posted by Daniel Holzman View Post
The reason your method would not work is that water does not act to consolidate sand. The placement method you describe is similar to hydraulic fill, which is commonly done using a high pressure slurry of water and sand, shot out of a hose, which fills the hole. This method has also been used to construct sand core dams, occasionally with tragic results, since the wet sand DOES NOT consolidate even when the water is drained, leaving it in a loose, weak condition, which can lead to unexpected future settlement.

If the fill does not need to be consolidated, because there is no construction planned above it, or the construction above it is lightweight or resistant to settlement, the method can and is used as a low cost alternative to conventional placement (with compaction) of structural fill.
I know nothing about soil mechanics. However, doesn't consolidation involve applying stress to soil while water is being removed from it? The weight of sand and water should apply the stress, and the drains will remove the water. I'd be interested in seeing data about settlement of sand placed with water which is then well drained.

I can see how erosion of a sand core dam can lead to failure, however in my application the walls and bottom of the pool should prevent erosion.
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Old 10-27-2012, 01:34 PM   #8
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Thumb, here we have a self described "newbie" wanting to fill a swimming pool with wet sand and a civil engineer saying not to do it. As you can see, I'm and idiot, I will and have argued with architects, but I usually agree with an engineer.
When masonry's rain and groundwater gets into the rubble filled solid walled pool the sand is gonna do all sorts of weird things, filtering down thru the rubble for one. You'll be recreating a cause of one type of "quick sand." ...." doesn't consolidation involve applying stress to soil " sand is not soil, sand needs something, silt or clay, to consolidate with.

I'm not a big fan of rubble fill, especially on smaller home projects, and especially with large chunks. You really need some experienced hands at using it and mebbee even a civil engineer overseeing it. If the voids are not filled it will never stop settling. In your situation, I'd break up sides and bottom, and spread it around, I wouldn't want to use pieces much bigger than I could handle by my self, mixed thouroughly with sand and soil, and mechanically vibrated and compacted.

Watch a road being built, they dig up the dirt, pack it back in, then pull plows and a sheeps foot over it, pack more in, tear it back up, pack it, tear it up over and over.

When you get a few feet from top its time to put up the sign; "Clean Fill Dirt Wanted." I used to wonder about that, how could dirt be clean?
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Old 10-27-2012, 01:45 PM   #9
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Sand Fill For Swimming Pool


This discussion about using sand for fill notes that it can't be compacted, but that it usually tests close to 100%: http://forums.jlconline.com/forums/a...hp/t-6429.html
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Old 10-27-2012, 01:54 PM   #10
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Thumb, here we have a self described "newbie" wanting to fill a swimming pool with wet sand and a civil engineer saying not to do it. As you can see, I'm and idiot, I will and have argued with architects, but I usually agree with an engineer.
When masonry's rain and groundwater gets into the rubble filled solid walled pool the sand is gonna do all sorts of weird things, filtering down thru the rubble for one. You'll be recreating a cause of one type of "quick sand." ...." doesn't consolidation involve applying stress to soil " sand is not soil, sand needs something, silt or clay, to consolidate with.

I'm not a big fan of rubble fill, especially on smaller home projects, and especially with large chunks. You really need some experienced hands at using it and mebbee even a civil engineer overseeing it. If the voids are not filled it will never stop settling. In your situation, I'd break up sides and bottom, and spread it around, I wouldn't want to use pieces much bigger than I could handle by my self, mixed thouroughly with sand and soil, and mechanically vibrated and compacted.

Watch a road being built, they dig up the dirt, pack it back in, then pull plows and a sheeps foot over it, pack more in, tear it back up, pack it, tear it up over and over.

When you get a few feet from top its time to put up the sign; "Clean Fill Dirt Wanted." I used to wonder about that, how could dirt be clean?
Thanks for the reply. My proposal is to not put rubble in the pool- just sand, and to provide good drainage at the bottom of the pool. The walls and sides remain. Just think of a five gallon bucket filled with sand with water poured onto the sand. A layer of filter fabric covers the bottom of the bucket which has holes punched in it. After the water drains and the sand dries, would the sand settle?
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Old 10-27-2012, 04:18 PM   #11
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Sand Fill For Swimming Pool


Your proposed technique involves placement of saturated sand, followed by drainage of the water from the sand. As long as the sand is saturated, the effective stress on the sand is low, and can be computed as the difference between the unit weight of the saturated sand and the unit weight of water. The typical unit weight of saturated sand is approximately 130 pounds per cubic foot, and the unit weight of water is approximately 62 pcf, so the effective stress on saturated sand is approximately 70 * depth of sand in units of pounds per square foot (psf). So at a depth of 10 feet, the sand would feel an effective stress of approximately 700 psf.

Once the sand is drained, the effective stress is equal to the unit weight of the moist (no longer saturated) sand times the depth of the sand. Moist sand typically has a unit weight of approximately120 pcf, so at 10 feet, the effective stress would be approximately 1200 psf, which is higher than for the saturated sand. Therefore, the sand would undergo consolidation under its own weight after the water is drained.

Unfortunately, the stress of 1200 psf at 10 feet is no sufficient to perform effective consolidation of the sand, so the sand undergoes a relatively small amount of consolidation compared to the full potential consolidation. When you put a building on the sand that has been partially consolidated, the sand undergoes additional consolidation, leading to settlement of the foundation of the building, with potential damage to the building.

The exact amount of consolidation that occurs under self loading of the sand is difficult to determine, but can be done by an experienced geotechnical engineer. This type of problem is why they go to college, and why you need a seasoned professional to assist you.

The other option is to compact the sand is small (typically 6 inch layers) as you go, using a heavy tamping device, a vibratory roller, or heavy equipment. In order to achieve reasonable compaction of the sand suitable for installing a building above, you need many thousands of pounds per square foot, far more than you get from self consolidation of the sand, but well within reach of typically available consolidation equipment.
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Old 10-28-2012, 04:18 PM   #12
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Here are the requirements for pool removal in one California city:

"The permittee must remove a section of the deep end having an area of at least 100 square feet. The sidewalls of the pool must be removed to a depth of at least 2 feet below finish grade. All debris must be properly disposed of off site. An inspection is required to insure that the above has been completed.
Backfill material may be uncompacted sand to the full depth of the pool wall. Exception: The top 24 inches may be topsoil or other similar material for landscape purposes. Backfill material other than sand must be compacted to a relative density of 90% and a soils engineers report, or records of proper compaction made by a recognized test lab (approved by the Building Official), must be provided for final approval. Inspection of the backfill material by the City Inspector is required."

http://www.ci.fullerton.ca.us/depts/...demolition.asp
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Old 10-28-2012, 06:13 PM   #13
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Sand Fill For Swimming Pool


Thumbhammer -

Learn to read a code requirements properly and understand it is not the best or preferred way, but a minimum standard to be followed before you are put in jail.

The minimum is fine as long as all you want to do if you want to watch the grass grow on the new dirt and are willing to occasionally fill to maintain a desired grade after settlement.

If any part of your enclosure is bearing on the filled area or if a slab is placed over it you are in a different world.

Just ask your local building inspector for an opinion - they do not like to deal with problems after a poor installation because it make their job more difficult for them and you to correct things if you find problems later.

Since the exception was in the codes, apparently the cheapest or easiest way caused it to be there since it took some reason for the effort to insert the requirements. Past problems guide the codes.

90% of proctor is nothing difficult to get and sometimes can be obtained by accident (using good materials).

It is good that you are trying abandon a well.

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Old 10-28-2012, 07:49 PM   #14
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Backfill material may be uncompacted sand to the full depth of the pool wall.
Thumbhammer, as Concretemasonry said this is a-ok if you want a yard ....

if you are attempting to place a building over it I refer you to the following from the 2009 International Residential Code which is the basis for the California Residential Code:

SECTION R403 FOOTINGS

R403.1 General.
All exterior walls shall be supported on continuous solid or fully grouted masonry or concrete footings, crushed stone footings, wood foundations, or other
approved structural systems which shall be of sufficient design to accommodate all loads according to Section R301 and to transmit the resulting loads to the soil within the limitations as determined from the character of the soil. Footings shall be supported on undisturbed natural soils or engineered fill. Concrete footing shall be designed and constructed in accordance with the provisions of Section R403 or in accordance with ACI 332.
uncompacted sand is not engineered fill. engineered fill is material used based upon a professional engineer's design for structural backfill when one cannot erect footings on undisturbed virgin soil
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Old 10-28-2012, 09:10 PM   #15
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Thumbhammer, as Concretemasonry said this is a-ok if you want a yard ....

if you are attempting to place a building over it I refer you to the following from the 2009 International Residential Code which is the basis for the California Residential Code:

SECTION R403 FOOTINGS

R403.1 General.
All exterior walls shall be supported on continuous solid or fully grouted masonry or concrete footings, crushed stone footings, wood foundations, or other
approved structural systems which shall be of sufficient design to accommodate all loads according to Section R301 and to transmit the resulting loads to the soil within the limitations as determined from the character of the soil. Footings shall be supported on undisturbed natural soils or engineered fill. Concrete footing shall be designed and constructed in accordance with the provisions of Section R403 or in accordance with ACI 332.
uncompacted sand is not engineered fill. engineered fill is material used based upon a professional engineer's design for structural backfill when one cannot erect footings on undisturbed virgin soil
It's interesting that there in no definition of "engineered fill" in the California Residential Code. (I don't live there, but that's beside the point.)

Section 401.2 requires that the foundation support the design load.

R401.4 Soil tests. Where quantifiable data created by accepted soil science methodologies indicate expansive, compressible, shifting or other questionable soil characteristics are likely to be present, the building official shall determine whether to require a soil test to determine the soil's characteristics at a particular location. This test shall be done by an approved agency using an approved method.

R401.4.1 Geotechnical evaluation. In lieu of a complete geotechnical evaluation, the load-bearing values in Table R401.4.1 shall be assumed

TABLE R401.4.1 PRESUMPTIVE LOAD-BEARING VALUES OF FOUNDATION MATERIALS gives sand a load-bearing value of 2,000 psi .


I interpret this to mean that a geotechnical investigation is not required, and that if the design load is less than 2,000 psi there should be no problem.

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