Building site prep and soil compaction

[Hay Dude]

If I could chip in with a few things from the other side of the world. Here in Australia my family have just completed a new house build on cut and fill. I have just punched some numbers into the metricator and we did over 50,000 square feet of cut and fill up, up to about 6foot high in places. We had a couple of contractors quote us with different sized machinery (it was to big a job for the 5035 Mahindra) Many insisted that track rolling by excavator and truck compression would be enough. In the end we went for a fantastic older contractor who gave us what I thought was very good advice.

The slab and building are only as good as what they are built on. For us it was reactive soil that needs lots of work to be stable. So it was worth putting some time and money into the base. Especially as we plan on staying for quite a while. The barn might have lower requirement than a home but I believe the principle is the same.

Tracked machines are really good at minimising their ground pressure and maximising their traction. If they track roll a site it comes up smooth but the deep compaction is quite minimal in comparison to specialist gear. The padfoot roller really only has one function and did it well for us.

Like many things the secret is a good recipe. The Mahindra did get a run on site as the tow vehicle for the 260 gallon water trailer. We used a fire pump and 2inch hose to spray the clay down and keep a wet texture. We would spray out before the dozer added a clay layer and spray as the roller worked. We tried to maintain a level of moisture like a bread dough where you could squeeze a ball in your hand and it held its form without being dripping wet. We only ever added about 6-8 inches in any one pass with the dozer. In hindsight for us this was a key. The layers bonded really well and later when we augered post holes and house pilings you could see and hear how strong the layers were as a whole or hole in this case.

We paid about$120 an hour for our roller on site. It sounds expensive next to your day rate but we only paid for machine hours. So when we had one operator on site our bill was broken down into so many hours bulldozer@$140, 20ton excavator @$135ph and roller. No operator wanted to be onboard the roller for hours. A water truck was supposed to be nearly $90ph and so the mahindra came through big. It worked out well until we had to pick up time and ran three operators. Impressive amount of soil gets moved, but every tick of the watch is accompanied by the sigh of a bank account crying.

Not sure I have helped with the decision making but I hope some info helps. For us it added to the cost to do it with the roller but the extra cost as a percentage of our house build was worth it to know we had the best prepared base under our home. Especially given how reactive our soils can be. As it turns out we have had our annual rainfall total in five months this year with winter not yet here so we will soon know it was worth it.

I threw in a pic to give you an idea of the scope of our fill

Good luck with the build, I love a good barn or as we call them Shed.
Cheers,
B.RView attachment 656942

We use a similar to that technique called “ puddling “. I built a garage around a razed smaller garage. I was concerned the middle of the slab, where the old structure was, would settle. I used the puddling technique and it worked perfectly.
It was used all the way back to the Roman Empire.

 

[Hay Dude]

A bulldozer will be fine.

I was putting in a road on my farm, and my Grandfather was backing the truck up, and he would go about 5 feet and then drop out of sight. After a few loads he got out of the truck and asked me how I was spreading the gravel, and I said using the excavator.

"no, no, no", he said, "Use the bulldozer, and use the tracks. Flatten the load with the blade then get in there and steer, steer, steer." The tracks grousers lock those rocks together and compact it like you would not believe.

The next load, he backed his truck all the way to the end of the gravel he had just dumped. I would not have believed my grandfather if I had not seen it myself.

Here in town, his roads have lasted 40 years. Roads where they have used excavator and sheeps-foot roller have only lasted 10 years before breaking up. Trust your contractor, he knows what he is doing.

I’d agree with you on roads, but a road can settle a few inches, and nobody would know. If a building slab or footings settle even an inch, itll cause all kind of problems. We can’t do that here in my area. Building inspector will fail any fill required to be compacted if tracks are used. Loose soil must be compacted in lifts if compaction is required on architect or engineers plans