# How much shrink will you get with compaction



## cdub

I'm estimating a little dirt project and I need to know how much shrinkage I can expect with 98% compaction. For easy math, let's say I have 10cy on a truck what will I have when it's compacted?


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## cexcavation

I always figure at least 20% with soil. If I have a bad feeling about it, I bump it up......it all depends since soils vary so much. 10 yards would compact to 8yds or less depending. That is how I do it, but that may not be correct. I'd love to hear what other guys use for a compaction factor.


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## dayexco

take a sample of the soil to a soils engineering firm...have them determine your maximum dry density...go from there. anything you hear form us will be bogus, we have no clue as to what soil types, moisture contents you're dealing with....and, i'm not a soils engineer!

fwiw.....when i'm dealing with a cohesive soil...i estimate a min. of a 33-35% shrink....granulars, min. of 25%


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## tgeb

It really depends on the material you have.

Can you get more specific cdub?

For the most part I think C's method would work well, as would Dayexco's guidelines.


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## cdub

I would call the material a silty clay. The material will be excavated from bank but the pay item is compacted fill. I'm trying to calculate production knowing the loose volume of my trucks but not the compacted volume. I've searched a little and found information to support both of you. I realize its a soil specific factor. I was just curious what rules of thumb you guys use. I would normally call a 15 yard truck 10 compacted, but I can't remember where I came up with that.


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## rino1494

Obviously it depends on the soil and the moisture content, but I usually figure 25%.


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## denick

As day and rino said 25% for granular soils. 33% to 40% in clay soils.


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## rino1494

What are you building and what is your method of compaction ?? 98% seems like a pretty high standard. We recently completed a building pad for a 53,000 sq. ft. building and it called for 95% compaction. 12" lifts, we were getting about 102 with our Cat CS553 roller. 

How much material are we talking about here. I wouldn't be too picky about percentage unless you are talking alot of material. As long as you are in the ballpark, you will be ok.


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## Blas

25 percent will get you really close in any soil. When I bid projects 25,000CY or less that is what I use. If I am going to move more than 25,000CY then I will take a sample to the nerds. :laughing:


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## cdub

It's an auxillary spillway repair on a lake. There is about 20,000 of compacted fill. The farthest haul is about 1000 feet and averages about 300-400 ft. I was planning on getting some sort of vibratory roller for compaction. I've got along real well with them compacting sewer trench backfill (100+%) if the guys will slow down and let it do its work.


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## dayexco

Blas said:


> 25 percent will get you really close in any soil. When I bid projects 25,000CY or less that is what I use. If I am going to move more than 25,000CY then I will take a sample to the nerds. :laughing:


i'm going to bid every "clay" job i can get my hands on...and sub it to you!!!


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## Blas

I guess I should have clarified a little more. Day hit the nail on the head with knowing the material you are moving. 25% would be a very crude example and would work for sand to sandy lean clay. If you are in a real plastic clay 35% - 40% wouldn't be out of the question. I wouldn't bid a plastic clay site with a 25% shrink factor, lucky for me this area is usually sand - sandy lean clay.


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## cdub

Blas said:


> I guess I should have clarified a little more. Day hit the nail on the head with knowing the material you are moving. 25% would be a very crude example and would work for sand to sandy lean clay. If you are in a real plastic clay 35% - 40% wouldn't be out of the question. I wouldn't bid a plastic clay site with a 25% shrink factor, lucky for me this area is usually sand - sandy lean clay.


 The 35-40% shrink is from loose form, correct? I figured 30% but I think my cycle times are slow. I figured it from the longer end of the haul to allow for down time and other work interruptions. 5% volume change could easily get absorbed. 
I appreciate the advice guys. Thanks.


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## cdub

cdub said:


> The 35-40% shrink is from loose form, correct? I figured 30% but I think my cycle times are slow. I figured it from the longer end of the haul to allow for down time and other work interruptions. 5% volume change could easily get absorbed.
> I appreciate the advice guys. Thanks.


10% may tickle a little.


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## denick

cdub,

If you need 200 cy to fill a hole of measured size. you need to dig 200 cy of dirt out of a bank. When you excavate it and dump it in the truck it swells to 270 cy at the 35% swell factor. You need to transport 270 cy. If you dump that 270 cy on the ground and compact it 100% it has a shrinkage factor of .74

All this depends on the material your digging is at a 100% compacted density. for that particular soil. if it was disturbed already and loosened it might already be in a swelled state. If the material that has been packed like iron for the length of a project and you start digging it it may swell at a factor X's 2.


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## rino1494

cdub said:


> The 35-40% shrink is from loose form, correct? I figured 30% but I think my cycle times are slow. I figured it from the longer end of the haul to allow for down time and other work interruptions. 5% volume change could easily get absorbed.
> I appreciate the advice guys. Thanks.



Obvisously we don't work 100% for a full day. On avg. I figure that we work 50 min out of every hr. So, when figuring jobs, I figure how much material can be moved per hr and multiply that my .83 to get actual.


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## Blas

I will post up a chart and some literature on the subject when I get around to scanning it. Probably tonight sometime.:thumbsup:


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## cdub

For my cycle times I figured the number per hour at maximum production then reduced that number by estimated dowmtime. I think that its a round about way to the same end.


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