weight in the truck doesn't matter as much as tire pressure. same psi.. same ground pressure. if the dump truck digs holes then any crack a concrete pad will sink right?. sand? i can see contained sand like to fill a garage that already has a footer and stem wall.
sand, near wetland area, over organic material, getting stuck/ sinking in the grass next to the fill area. i'm just the metal guy on the sites i go to, but thats all a no go around where i'm at. around here all organic would be pushed off and filled with large 1.5" crush rock in steps and real deal/ bomag compacted.
I didn't really get good pictures of it, but I scraped all the organics off of where I'm building and piled them up at the bottom of the site. There was a 4-16" layer of topsoil and construction waste (pipe, appliances, bricks, 2x4's etc.) that I removed and got down to the clean sandy hardpan. It's a bit of a grey area if you're supposed to disturb topsoil and roots before placing fill near a wetland so I did my best to make it look like it didn't happen and filled in the removed area with sand up to the level of the surrounding topsoil and slightly onto the grass. When I got stuck I had backed too far away from the fill and buried it in that layer. The swamp/wetland area was a borrow pit made by the builder of the house to get sand for the rest of the site and then he set up culverts to it to get it water moving through it for a water feature and drainage of the rest of the property. So it's not like it's completely bottomless loon shit, it's 16" of bottomless loon shit.
I will likely be spacing the building farther away from that northeast corner than I had originally planned just to be safe. I'm going to build it up and fill it in like I it's getting a slab on it but it's more likely that I'll stay 8' of build able area away from the edge and build a lean to on it after a few years.
After another 34 yard haul, spread, roll with 10,000 lb water truck on bald treadwrights, 2 plate compactor passes last night it seems like it should be firmer but it's pretty hard to tell just looking at the surface. After another 100 yards or so I should be able to get the dump truck on most of the site as I build up. I can just now consistently get the loaded dump truck (50,000lbs) on the first 20' of the south edge without constantly getting stuck and it does seem to be firming up in that area after I level out the ruts and run the plate across it and then put the dump truck on it again. I'm doing passes straight, and then crisscross. When doing my axleshaft pound test it's still about the same as the undisturbed soil where I'm digging so it may just all be in my head.
I've called a few places and so far nobody has a Bomag available around here for the rest of the year, everything's booked till next summer. I think that at this point I'd be better off getting it all hauled and packed as good as I can with the 10k truck, 50k truck, and plate in small lifts now and letting it set over winter rather than trying to find a bomag in the spring and miss out on the 9 months of settling and temperature swings. Hands down a bomag would be way faster but if I stick to 4" lifts and let it set all winter I can't see what the difference in final compaction would be. Lots of garages and houses are built around here like this. The sand I'm using is what they use as base for class A road beds around here (their pit is about 1500ft from mine), then they top it with rock before paving and they cover the slopes with topsoil.
The biggest thing to watch for around here that will cause damage to a slab is building on clay or other moisture retaining material that heaves when it freezes and that will pulverize a slab. Settling on poorly compacted fill is of course a cause for concern but to be honest I've seen garages built on sand on similar fill sites with a lot less attention paid to compaction until the final 12" or so and they never had any serious issues.
One variable I haven't decided on yet is to do a floating slab or dig down and put in footers. I'm compacting as good as I can everywhere for now, so that doesn't really affect what I'm doing now, but something I'm going to have to consider.
