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Discussion Starter · #1 · (Edited)
What is the best way to compact wet clay to 95% mod that is being dumped on a site that has the water table just a few feet below the surface. Not to mention that this is the wettest time of year in louisiana. I'm building a house pad and the homeowner needs to pour the slab in the beginning of january. The lot is flat with pipelines running along the only two sides with a ditch and the the pipeline company won't let me cut ditches across there pipeline to help with drainage. I'm trying to not use lime because I don't have a stabilizer. I'm looking for tricks of the trade that I may not know about. I have a dozer, excavator,tractor with discs and dump trucks. I'm trying to purchase a padfoot compactor.
 

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I hate to say it but I see no way you will get 95% compaction with wet clay. All it will do is pump no matter what size roller/compactor you use. Usually, the compaction will draw the water to the surface or at least it does here in Atlanta with the red clay we have.

In the situations like this, we have had to over excavate, lay fabric down, lay with stone just to build a stable base and then refill with dry compactable soil. Hope it helps.

BTW, go to introductions and introduce yourself...

There are certain things that can be added to soil to help dry it out but not sure it will help with the water table that high.
 

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Why can't you use a different material ?? Mix in some sand or fly ash to help choke it up. Ground heaters with frost blankets help dry out mud fast. One way or another, it is gonna cost money.
 

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Discussion Starter · #5 · (Edited)
The only place that has sandy material is from the banks of the mississippi river. But the river water level is higher than the borrow pits. So I may have to wait for the water level to come down, which it already started coming down this week.
I think I'm going to cut some 2' deep trenches every 20' in and around the pad site so that when I start tracking on the material the ground water will be able to flow into the trenches and not pump up into the fill that i'm going compacting. Then I'm going to stock pile the fill material in-between the trenches and disc it to dry it. as the fill material dries out I will cut the top dry layer off and use it in 6" lifts to get my compaction. Hopefully as I'm compacting it the ground water will go into the trenches and not up into my fill. Then I will have to muck out the trenches and backfill and compact them last. If anybody has a better idea that 's affordable, I'm open. As with all clients they can't see why there pad is going to cost more and take longer than there friends pad that was built in july. They also have a inlaw that is a very good carpenter that is telling them how easy it is to build a pad and he doesn't see what the problem is.
I'm sure everybody on this forum has dealt with the brother inlaw, uncle, coworker ect, ect,ect that knows more than the people that have been doing this for years.
The Smart thing to do would be wait until the conditions are better. But I'm going to try to get this pad to pass compaction for a reasonable price. They just don't know how hard it's going to be.
 

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I'd watch out if I were you. I've never seen wet clay get compacted well. On top of that it sounds like your clients won't want to pay more to get the job done right.

That's a bad combination. Good luck.
 

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I live in clay country out here on the West Coast, and there is one word you will have to use a lot........ROCK. Over excavate, dig an outlet trench or two to relieve any surfacing water to elimante ponding. Lay down your geotextile and build her back up to grade starting with big rock and graduating to smaller crushed as you go.

As Rino stated, throw some smaller rock down prior to the fabric to get the clay to bind up some as well as help support the fabric in the case of any voids.

One way or another, you will need to bridge over the clay and allow for separate movement of the pad as compared to the clay. Clay is extremely expansive as you are aware, and you don't want that pulling your foundation apart.

The straight answer is spend the money up front and do it right. One other note is to keep the machines off it until you have enough rock to begin bridging the weight, otherwise you will pump it up and have to start all over. Just my 2cents.....good luck
 

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If the ground water is that high, why not set up a sump to keep pumping from.
 

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If the ground water is that high, why not set up a sump to keep pumping from.

You sound like an engineer!!!:laughing: Engineers often forget that gravity is free and dependable:thumbsup:

I had an excavation a few years back, and amazingly there was a gopher hole on the bottom side. I thought maybe it would work, maybe not, but I directed my flow to it. Came back the next day after all night rain, etc. and that gopher hole was still taking all the water you could throw at it.:thumbup:

In short, pumps are a pain if you ask me. They are necessary at times, but if I can ditch it out I will.
 

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IMO, you'll never get wet clay that you've brought into a wet site to 95% SPD on its own.

Ideally you'd use something other then clay, some dense graded aggregate or at least bank run or even sand.

If you must use clay then definitely perform shallow lifts with a sheeps foot as planned but also spread and compact a large crushed aggregate into your lifts. 2.5-3" crushed limestone, which seems to be available in your area as 3x1 Stone would help to stabilize the soil and reduce pumping. If the clay is sloppy wet I would spread fly ash to dry it out.
 

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You sound like an engineer!!!:laughing: Engineers often forget that gravity is free and dependable:thumbsup:

I had an excavation a few years back, and amazingly there was a gopher hole on the bottom side. I thought maybe it would work, maybe not, but I directed my flow to it. Came back the next day after all night rain, etc. and that gopher hole was still taking all the water you could throw at it.:thumbup:

In short, pumps are a pain if you ask me. They are necessary at times, but if I can ditch it out I will.
He said that the lot is flat and he cannot cut ditches because of the pipeline. Yes pumps are a PITA but you gotta do what you gotta do. If the groundwater is really bad, you can create a siphon system to drain the area, that way you do not have to babysit pumps overnight.
 

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He said that the lot is flat and he cannot cut ditches because of the pipeline. Yes pumps are a PITA but you gotta do what you gotta do. If the groundwater is really bad, you can create a siphon system to drain the area, that way you do not have to babysit pumps overnight.
Yeah, it would probably help if I actually read the post with my brain turned on!!!:party:
 

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Discussion Starter · #15 ·
How do ya'll feel about a 3ft thick sand only pad? The sand we have is a silty sand mixture that is pumped/dredged from the mississippi river into borrow pits. The sand drains well and compacts easy but when you dig the footings they have to go 1ft into natural soil. The sides of the footings can collapse if the sand dries out to much. With the vapor barrier in place I won't be a ble to use a sprinkler to wet it again. I'm worried that the concrete finishers will walk to close to the edge of the footing and cause it to cave in.
 

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i think rino gave you a pretty good idea....dump in some perimeter drains...get the moisture out of the existing soil...you start putting dissimilar soils on a project, if you're subject to freeze/thaw...their shrink/swell factors will be a LOT different. either you want all of it to move, or none of it.
 

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How do ya'll feel about a 3ft thick sand only pad? .......but when you dig the footings they have to go 1ft into natural soil. The sides of the footings can collapse if the sand dries out to much. With the vapor barrier in place I won't be a ble to use a sprinkler to wet it again. I'm worried ........... cave in.
Do a footing and stem wall on the natural soil, backfill with and compact the sand fill.

i think rino gave you a pretty good idea....dump in some perimeter drains...get the moisture out of the existing soil...you start putting dissimilar soils on a project, if you're subject to freeze/thaw...their shrink/swell factors will be a LOT different. either you want all of it to move, or none of it.
I Agree.

But,
He is in Louisiana, I don't think freezing is an issue.....but I have never been there in the winter time.
 

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Get some lime, mix it in, about 4' deep or so it'll dry out the clay and compact very well if you use enough of it. Then hurry up and pour the slab b4 the ground water intrudes.
 
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