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Thread: compacting dirt

  1. #1
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    compacting dirt

    I have a small area that I want to fill in and put a building on it. The area is about 80 feet wide and 200 feet long and maybe 10 feet deep at the lowest point. This is not a wet land area. How much dirt can you put over an area before you need to run a compactor over it? I was thinking about putting dirt in the area with dump trucks. Then bladeing out the dirt and pulling a compactor over it with a tractor. I would think the top 4 feet would not need to be compacted because a basement would go down about 5 to 6 feet. Does this make sense to you guys or do I need an education? This would be a job for summer, too cold now. Thanks for any suggestions.
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  2. #2
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    You need compaction in all of the fill. Scarify all the original terrain several inches to prevent a shear plane. Build your fill level.

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    Back filling for a building pad we always did 1 foot lifts and watched the moisture.

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    Thanks mtbox and stump knocker. How do you do the actual compaction. Do you criss cross or always run in the same direction? Do you run the compactor over the ground until every square inch has compaction prints on it. The machine you could pull behind a tractor, is it called a sheep's foot. Do they all hammer or vibrate when they are pulled over the ground? As you can tell I don't know the correct way to do it but it can't be too difficult if you are told how to do it.

    Stump knocker, what do you mean by watch the moisture?
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  5. #5
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    Orville, Here in Fl. we only have sand!!
    WE usually used a loader to push the fill and a loaded bucket to compact.
    You can't get density with dry sand.
    What type of material are you going to use for fill?
    I have no idea what your fill dirt will be like in MN.
    A cheap way is check density is a pointed steel rod with a handle.
    Doesn't take long to figure out if your fill is compacted.

  6. #6
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    You obviously have experience, I don't. There is a high area close to the low area and there is sand there. I thought you had to compact all soils so they would not settle. There is a couple of feet of light clay above the sand.
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  7. #7
    Super Moderator CM1995's Avatar
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    What are your local codes and ordinances that pertain to building construction? Will your local building department/inspector require compaction testing before you footings/foundation is poured? This is important information that you need to know before starting construction.

    For a project this size I would highly recommend getting a dirt doc involved, commonly know as a geotechnical engineer. Don't be overwhelmed by that, most dirt docs are a little weird (I guess it comes with the profession ) but good folks and not that expensive, especially when you compare their fees % wise to the total cost of the project.

    The dirt doc will get a sample of the fill material you want to use and run a proctor and shear test on the material. The proctor will tell you the optimum moisture content and the particle make-up of your fill material. This is important as it varies with every soil type. They use this information from the soil test to determine when the material is compacted to the required spec's - 95%,98% or whatever your requirements are. The shear test will tell the dirt doc the angle of repose, which is the angle the material can be placed at and remain stable. This is only an issue if you are filling on or creating a steep slope.

    The dirt doc can also tell you the height each lift needs to go in. From my experience, most of our soils work best in 8-10" lifts, your soils could be totally different. As you place and compact your lifts, your dirt doc will send a tech out to pop a couple of nuclear density tests and tell you whether or not the material has been compacted to spec. They will perform these tests on each lift after you have compacted it.

    Your local building department/inspector will probably require these tests and reports before allowing the foundation to be place. Once again, check with them first.

    Compaction -

    Compaction can be achieved through various methods. What kind of compaction equipment do you have available? For compacting soil a vibratory sheep's foot roller works very good but in reality a dozer, skid steer, backhoe, etc. can attain this, it's just a matter of time and what you have available. Another method we use with our heavy clay soils is a loaded tandem dump. I have compacted many a lifts and achieved specs with a loaded tandem or tri-axle. Alot of times a loaded tandem is spec'd to check sub-grade before base can be laid on streets and roads in my area.

    It's very important to use fill material free of topsoil, roots, vegetation, large rocks, debris, etc. This will keep the lifts uniform and make a stronger foundation.

    Good luck with your project!
    Last edited by CM1995; 12-12-2011 at 09:46 PM.
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  8. #8
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    I did not know that compacting dirt could be that much of a science. Many years ago a dirt guy bragged that they could compact dirt better that the glacier. It does look like something I should not just jump into. thanks
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  9. #9
    Senior Member heavylift's Avatar
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    I worked with dirt many years, we had sand that you could NOT use a compactor on, wouldn't pass no matter what we did, finally we just dumped a load of water on it, Inspector tested, it passed.. the vibrating or even the movement of the vibrator destroy the compaction.

    sometimes just rolling will get you compaction , other times it seems like an eternity to get compaction.

    Mostly it depends on the soil type.

    Around here clay is almost never used as a build pad material, it is expansive and will swell and shrink. Most now use what we call LOW VOLUME, which means there is very little clay in the material. More or less it is what they dig off the top of the sand pits here, a sandy dirt.

    Worked with soil with moisture as high as 42%, a sloppy mess.. but that was the spec.
    The engineers test the soil for optimum moisture. the design the specs around that, and other stuff..

    The absolute worst is the modified proctor. which is a nearly impossible to obtain the compaction. This is seldom used around here

  10. #10
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    Quote Originally Posted by heavylift View Post
    The engineers test the soil for optimum moisture. the design the specs around that, and other stuff..

    The absolute worst is the modified proctor. which is a nearly impossible to obtain the compaction. This is seldom used around here
    What are the Dirt Docs using in your area to determine optimum moisture and compaction specs?
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  11. #11
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    Can really say other that if we don't get compaction, or are having trouble, they will get another 5 gallon bucket of material to test. Sometimes the tester will have 20 to 30 jars of sample to match the soil to determine which proctor to use at the site.

    "We'll run another proctor test"


    I used to do it for awhile, shake it thru sieves and cook the stuff, that was for the quality of the material, I think such as rock and sand. Beat in to a mold, was for asphalt and dirt but that was over 30 years ago. can't even remember what we did then. or if they even do it that way now

  12. #12
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    Quote Originally Posted by CM1995 View Post
    What are your local codes and ordinances that pertain to building construction? Will your local building department/inspector require compaction testing before you footings/foundation is poured? This is important information that you need to know before starting construction.

    For a project this size I would highly recommend getting a dirt doc involved, commonly know as a geotechnical engineer. Don't be overwhelmed by that, most dirt docs are a little weird (I guess it comes with the profession ) but good folks and not that expensive, especially when you compare their fees % wise to the total cost of the project.

    The dirt doc will get a sample of the fill material you want to use and run a proctor and shear test on the material. The proctor will tell you the optimum moisture content and the particle make-up of your fill material. This is important as it varies with every soil type. They use this information from the soil test to determine when the material is compacted to the required spec's - 95%,98% or whatever your requirements are. The shear test will tell the dirt doc the angle of repose, which is the angle the material can be placed at and remain stable. This is only an issue if you are filling on or creating a steep slope.

    The dirt doc can also tell you the height each lift needs to go in. From my experience, most of our soils work best in 8-10" lifts, your soils could be totally different. As you place and compact your lifts, your dirt doc will send a tech out to pop a couple of nuclear density tests and tell you whether or not the material has been compacted to spec. They will perform these tests on each lift after you have compacted it.

    Your local building department/inspector will probably require these tests and reports before allowing the foundation to be place. Once again, check with them first.

    Compaction -

    Compaction can be achieved through various methods. What kind of compaction equipment do you have available? For compacting soil a vibratory sheep's foot roller works very good but in reality a dozer, skid steer, backhoe, etc. can attain this, it's just a matter of time and what you have available. Another method we use with our heavy clay soils is a loaded tandem dump. I have compacted many a lifts and achieved specs with a loaded tandem or tri-axle. Alot of times a loaded tandem is spec'd to check sub-grade before base can be laid on streets and roads in my area.

    It's very important to use fill material free of topsoil, roots, vegetation, large rocks, debris, etc. This will keep the lifts uniform and make a stronger foundation.

    Good luck with your project!
    Great explanation CM1995 ! Well put. I think the books call for a tandem ( or 10 wheeler dump ) weighing 44,000 lbs or better , when "wheel rolling ". If we wheel roll, i just fill the old Pete. with dirt and go at it . Just remember to keep your lifts as level as you can, it makes life easier.

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  13. #13
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    we use what is called "Proof Rolling" to test the subgrade of a road. we use a loaded 4000 gallon water truck. I think the spec is 1" or less of ruts in the soil.

    wheel rolling usually won't get the higher percentages of compaction. It all depends on the types of soils that are being compacted.

    I had them test the 247 cat CTL once to see what it did on compaction ... 85%.

    Did do some digging in an old part of town. An island that was built with donkeys and carts. Those one billion hoof prints were very hard, almost rock like. Sometimes you could pick out the various loads of dirt that the carts had hauled.

  14. #14
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    Quote Originally Posted by dirtmonkey View Post
    Great explanation CM1995 ! Well put. I think the books call for a tandem ( or 10 wheeler dump ) weighing 44,000 lbs or better , when "wheel rolling ".
    Funny story now, frustrating situation then...

    We had a greenhorn dirt doc on a job doing a proof roll for a residential street. Standard practice around here is to use the first load of aggregate base to proof roll on the day you will be dumping base on the whole street. (Of course we always make sure the sub-base is good to go before base is scheduled) Back to the story, the first load of base shows up in a tri-axle and the dirt doc won't accept a loaded tri-axle to do the proof roll (we can gross 85K or so in Alabama with a tri) even with the lift axle up because the book called for a loaded tandem... We tried explaining the basic laws of physics to this guy but ended up having to get a tandem in and yes, it messed the day up.

    Quote Originally Posted by heavylift View Post

    Did do some digging in an old part of town. An island that was built with donkeys and carts. Those one billion hoof prints were very hard, almost rock like. Sometimes you could pick out the various loads of dirt that the carts had hauled.
    I don't know if it's true or not but I heard the term "sheeps foot" compactor originated from when the Romans would corral their sheep on the roads they were building to let their hooves compact the soil.
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  15. #15
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    If its mostly sand dont even wste your time with a sheeps foot as i have found they dont work at all, if its sand wheel rolling or a smooth drum roller works best in my experince. Now if its mostly clay thats where a sheeps foot does best, wheel rolling will also get good compaction also.

    And start your first lift with the best materila you can find, and i would also put the first lift in at around 2ft, if you dont do your first lift right and get compaction you will fight all the next lifts! That first bridging lift is crucial

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