How well does a trench compactor work with sand?

[1320stang]

I had to dig out some rock for my shop foundation, I have sand, some sandstone. No clay. Engineer said I need some separation between the rock and foundation. Concrete guy wants it backfilled and compacted to dig. I'm trying to keep costs down with my own labor.

 

[mike93lx]

Sand doesn't really compact well but a vibratory compactor will do the best possible. Needs some moisture as well

 

[PCustoms]

I had to dig out some rock for my shop foundation, I have sand, some sandstone. No clay. Engineer said I need some separation between the rock and foundation. Concrete guy wants it backfilled and compacted to dig. I'm trying to keep costs down with my own labor.

Sand is not the proper fill here

 

[mm08822]

Crusher run = stone dust up through 3/4 gravel blend. Use water when compacting. Do it in small lifts.

 

[1320stang]

Sand is not the proper fill here

I know, but it's what the whole back yard is made of.

Structural engineer designed 5" slab with #3 16"o.c. 16x22 perimeter footing with 4 #5 (2 top, 2 bottom) and #3 stirrups 32"o.c. 4.5'x4.5'x22" spread footings in the corners with #5 16" o.c. top and bottom, 5.5'x6'x22" spread footings at center column with #5 top and bottom as well as hairpin and 2 #5 side to side at center. I've got $3k in rebar on the trailer now.

 

[PopcornSutton]

Did you remove rock in order to get the footings to depth? That's what it sounds like since the concrete guy wants to dig through fill for the new footing. I can understand having a separation where rock was removed if it were a utility going in, but for a footing? Pay the concrete guy for the extra concrete and fill it.

By the way, before the present day nuclear density testers for compaction, the tried and true method was using a "sand cone". Dry fine sand will flow into every crack and crevice for 100% density.

 

[Pompey]

My guy put down this...
"Processed fill," often called "screened fill," refers to fill material that has been processed to remove large rocks and debris, resulting in a more uniform, compactable mix of soil and smaller aggregates, suitable for leveling, backfilling, and creating stable foundations.

 

[1320stang]

I was finishing up today (I THINK I HIT DIAMONDS!!! J/K) to get about a foot of clearance beyond the footing. That shelf goes down about another 6" as far as I can tell because the jackhammer buries itself quickly. Approximately 3' thick. The top of the shelf will be the elevation of the bottom of the 5" slab, the dark hole below the quartz is about the diameter of a thumb. I didn't measure but I think the chisel was 1.5" wide.

So we have quite a few earthquakes from the waste water injection wells disposing of frac water. They must pressurize those at a MUCH higher pressure than facing a well, my dad started pumping water to frac wells in '76 and I've been on tons of sites and where I lived, you couldn't swing a telescope more than a couple degrees without seeing a pumping unit before the horizon. Wasn't until the mid to late 90's that was ever had quakes bad enough to hear or feel. About 15 years ago we had one that felt like someone's foot slipped off the brake when you were standing in the bed of a pickup, or on a hay deck, and I was standing in my garage.

We got about an inch of rain Friday and Saturday so the ground got a good soak, but the gearing in the 8n and lack of weight just causes wheel spin if you're not careful. I started our just driving in circles to get some compaction.

 

[PCustoms]

We got about an inch of rain Friday and Saturday so the ground got a good soak, but the gearing in the 8n and lack of weight just causes wheel spin if you're not careful. I started our just driving in circles to get some compaction.

Sorry to be the bearer of bad news, but it sounds like you have ****** soil and running an 8N on top of it really isn't compacting anything in a structural sense.

Good luck.

 

[1320stang]

Hell I know that, if I rent the trench compactor I'd planned on running it over the whole site. I'm using the hand I'm dealt, I don't have an unlimited budget. Digging out and bringing in better stuff isn't just dumping in on the pad site, I'd had to dump it along the street and haul it all in with a skid steer or a better tractor. I can't bring in a dump truck on my 4" driveway, I'm already having to have the concrete pumped (told my wife you start at the back and work your way out but NOOOO!!!). Then I have to clean up the remnants of the fill along the street. You act like everything is a perfect scenario and it's not. I'm making the best of what I have with the budget I have. I've had the analysis done by a registered structural engineer even though I have no requirements from the county for one. No building permit, no inspections,

 

[PCustoms]

I'm sorry, you asked for advice and I was trying to politely provide some feedback.

Good luck, hope you get to enjoy your shop soon.

 

[1320stang]

Ended up getting a jumping jack as they didn't have a trench compactor and I did it in less than 6" lifts. Worked great, you can tell driving the tractor over it vs non compacted sand. Could it be better? Yes, but it'll do.