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Trench compaction

Palmer78

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Sep 14, 2008
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133
Location
Valley Springs, CA
Can you generally achieve 95% compaction using a jumping jack if you beat the hell out of it and put in maybe 6 inch lifts? I'm not quite sure of the soil type.
 

CM1995

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Yes go with 4-6" lifts max.

Depending on site factors like depth, width and length of trench and the spec's, I find that most of the time it's cheaper to backfill with stone as time and labor can get expensive manually compacting a trench.
 

d4c24a

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Jul 14, 2006
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753
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ENGLAND U.K
foam

foam concrete is the way to go :D most of our trench work in the road is done with this ,no sinkage
 

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CM1995

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Foam concrete? Never heard of it, how does it work?
 

Dozerboy

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TX
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Depending on the trench size and how good your operators are you can fill a trench pretty fast with a jumping jack. I have never had any trouble getting 95% with 6" lifts.
I only use them in small tight areas that other methods won't work.
 

d4c24a

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Yeah I found that site too with a quick google search. I was more interested in d4c24a's hands on experience filling trenches in the street.

basicly its a weaker mix of concrete using a foaming agent ,can be dug out fairly easily with an excavator ,very much like an aircrete block
when dispatched its very much a slurry mix ,and runs into all the voids /cracks etc that you cannot get via normal trench fill / compaction
when backfilling with stone on a class A road the tarmac will need to be 360mm thick ,when using foam its 100mm ,10/15 minutes to dispatch 16m3
2 days ready for tarmac

before and after pictures
 

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mally

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Dec 20, 2008
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Northern Maine
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supervisor
We call it flow-able fill up here. A low strength high air content concrete mix, basically sand and cement that is supposed to be easy to excavate. I have never used myself. We cannot use stone here although it would be so much faster and cost effective like CM says. We have to use all the same native materials back in the trench due to the severe frost action. Jumping jacks are slow and a pain in deep trench fills but you can get compaction for sure.
 

CM1995

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basicly its a weaker mix of concrete using a foaming agent ,can be dug out fairly easily with an excavator ,very much like an aircrete block
when dispatched its very much a slurry mix ,and runs into all the voids /cracks etc that you cannot get via normal trench fill / compaction
when backfilling with stone on a class A road the tarmac will need to be 360mm thick ,when using foam its 100mm ,10/15 minutes to dispatch 16m3
2 days ready for tarmac

before and after pictures

Thanks for the info. I have used flowable fill for the undercut portion of building footings before to get to sub footing grade. It's basically a 1500 PSI lean mix which is cheaper than standard 4K psi mix. It's probably the same as mally mentioned but but I think we're talking about two different products, as the flowable fill is more like standard concrete, albeit a lower strength but not easily dug out with an excavator.

In a roadway repair like the pictures you posted, I can see where that would be the pocket on the shirt. It gives good support for the roadway and can be dug out later if need be.

Most of my work is new construction, rarely in an existing roadway. The physics work differently when talking about settlement between the two and I see where this product would be very beneficial on two counts - being able to dig through it and limiting the risk of the trench settling in a road way.
 

Acivil

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Jan 30, 2010
Messages
154
Location
Tennessee
I have used flowable fill with compressive strength as low as 800 psi (as best I recall) in an application that would have to be dug or cut later, most batch plants have 2 or 3 mix designs for flowable fill depending on the application. I think you can pass densities with a jumping jack installing 6" lifts, but I would be willing to bet that if you installed a 6" lift, compacted, then cut the top 2 inches off you wouldn't have 98%... just my hunch, I've never tested it but its been my experience that it can be tough to properly compact a 6" lift with walk behind tamps other than the larger reversible type.
 

Ronsii

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Jun 26, 2011
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Western Washington
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s/e Heavy equipment operator
We have no problem getting 95%+ using type 17 or even some native in the seattle area verified with nuke testers and various depths with jumping jacks... but it can take some time if you have large areas to cover.
 

d4c24a

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ENGLAND U.K
Most of the aggregate used on these jobs are recycled materials ,shingle ,stone and also the aggregate for the foam mix
with contractors now having to guarantee their reinstatement for life ,the regulations on hand, arm, body vibration it is becoming more common to use

the cost difference in materials over say 100 metres of trench is very close ,but add in the time and labour saving and lack of compaction issues makes it a great alternative

we generally try to have enough trench open for two loads ,the truck carries enough cement for two loads ,so usually a grab truck will accompany with another load of aggregate on ,reload the batcher truck ,then take a load of dirt to the recycling station
fully loaded it runs at around 42/44 tons depending on the manufacturers design weight of the chassis

cheers graham
 

xrlentau6

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Jun 20, 2007
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88
Location
South Australia
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Desk bound and needing to get outside
All very intresting, I have untill recently only ever back filled trenches with sand, and then rubble (about a 20mm stone) and often used a leg rammer or dpu. Have always found the main problem we have is moisture, not having enough moisture in the material will mean no compaction. It does tend to be pretty dry and hot here.


On the current project I am working on we are at times using a lean mix, but not sure of how the costs work out.
 

tylermckee

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Jan 9, 2006
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768
Location
washington
I have backfilled sand in 18" lifts, couple passes with the jumping jack and never had a problem hitting 95%+. Material and moisture content is key.
 

CM1995

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Alabama
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Running what I brung and taking what I win
I have backfilled sand in 18" lifts, couple passes with the jumping jack and never had a problem hitting 95%+. Material and moisture content is key.

Using sand to backfill in my area would be very expensive. It's always interesting to learn how folks work in other areas.
 

joispoi

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Mar 1, 2008
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1,284
Location
Connecticut
Using sand to backfill in my area would be very expensive. It's always interesting to learn how folks work in other areas.

Here will have fill grade sand which is cheaper than masonry sand....make that "less expensive". It's unfit for mortar, but it's still not cheap.
 

CM1995

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Running what I brung and taking what I win
Here will have fill grade sand which is cheaper than masonry sand....make that "less expensive". It's unfit for mortar, but it's still not cheap.

Closest sand pit is at least a 2 hour round trip. A 25 ton load of sand will cost double what 25 tons of 8910 or 57 would cost per load delivered. Crushed limestone is abundant in my area and relatively cheap. You can buy waste rock for around $4 a ton but it's waste, only suitable for selective backfill above the pipe not bedding.
 
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