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.
depends on the soil but yes, you should easily get that.
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.
foam foam concrete is the way to go most of our trench work in the road is done with this ,no sinkage
Foam concrete? Never heard of it, how does it work?
More importantly how much does it cost?
http://www.foamconcrete.info/index.html
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.
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.
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
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.
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.
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.
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.
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
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.
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.
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.
CDF (Controlled density fill) 35% cement 65% sand is one mix we use, I also think there are several variations of the sand/cement combinations, but that seems to be the standard I get when ordering CDF. I have been told by inspectors and in the specifications that pea gravel is the only material besides CDF that does not require compaction. I use that in special applications like a vault that I will need to access to 6 months down the road, since it comes out easy with a vactor truck. It is more pricy than CDF counting placement. I like CDF because I can back fill a ditch quicker, with less labor and less question by inspectors. One person can backfill the ditch while the digging equipment is still digging and moving ahead. Thus, progress keeps moving on and a second machine is not tied up back filling in small increments. Back filling with compactable material seems to be a minimum of three people one placing material in the ditch however you do it, two people in the ditch one with a compactor and one with a shovel flattening out the high spots. Moreover, I repeat, in the ditch with all the BS that trying to work in a ditch entails. Having one person walk down the ditch line steering a chute on a barrel truck is so much faster. The CDF is cheaper that the total cost of labor. Around here, even non-union work gets charged out at $90+ an hour to the customer. The cost of an operator and machine is way past that. :my2c
I am late getting here, but my question is. How deep can one safely work a jumping jack in a trench. From what I understand anything deeper then 4' needs to be cut back. If I am compacting a 5'x16" trench in 12"-16" lifts that puts me around 4' feet for the first lift? Is this still considered safe? I have done it before, and it always feels a but marginal to me. I am just wondering what others feel is safe? Will
OSHA says 5'. At 5' and above it has to be sloped 2 to 1 or shored. To slope steeper than 2 to 1 it has to be approved in writing by a registered engineer. At 5 ft and deeper you need to have access within 25 ft of travel, translates to a ladder every 50 ft. While most 5 ft trenches are OK I would never be down on my knees in one. Trench cave ins are the second most construction site killer in the US next to falls.
I agree old-iron. Trenches are dangerous and should be treated with respect for the damage/killing they can do. This is a means and methods procedure but this is how we do it and of course varies considerably as this method can't be used all the time. Since we are always on a new construction site, we have the room and leeway to do this way. The most common sized storm pipe we lay is 18" to 36", depths range from 3' to 7-8', average would be 5' deep or less. Most of the time the storm line is in a parking lot or other paved area and compaction is very important. I like to excavate the trench to depth and cut back the sides, stair stepping them as needed to keep the main or bottom trench no deeper than 4' from the first bench, usually it's 3' or so. Running a 42" bucket usually gives enough room to lay the pipe in the bottom or main trench and a 4' wide bench on either side as depth requires (a 42" bucket with side cutters will cut a 4' swath). The bench gives you a place to carry the pipe laying tools forward as you go and is easier to get in and out of the trench and lay the pipe. This solves two purposes, the most important being safety and the other achieving adequate compaction over the pipe. If the line is in a paved area, backfill to the top of the pipe with #57 stone as it flows easily and fills the voids around the pipe. When we go to backfill, place 12 to 18" of dirt over the pipe and run the 533E over to compact it. The is where the previously cut bench allows the roller to get a full width in the trench and thus a more homogenous fill layer over the top of the pipe, tying it into the surrounding soil.