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What foundation for under 9-12,000 bushel hopper bins

18K views 22 replies 17 participants last post by  Duchek 
#1 ·
Thinking about buying a few hopper bins with skids. Have a clay soil that shrinks and swells as it gets wet and dry. My 1620 wheatland fertilizer bins with 10" of gravel under the skids will shift and require leveling about every 8 years. Seems like the south side of the bins thaws first in the spring from the sun.

Wondering what I would need for larger hopper bins with steel skids? Thicker gravel? Thin cement pad under the steel skid? Thicker cement donut under the steel skid?

Flat bottom bins are easy as they spread their weight out quite well. Hopper bins put a lot of weight in a very small area around the outside of the bin.

Are larger hopper bins better or worse for supporting? A bigger diameter would look to be more stable, but also more weight because the bin is usually larger.

I have heard of a few falling over, but never got a good reason as to why? Structural failure or poor site prep.
 
#2 · (Edited)
EDIT. Misread.

I would get specs on the recommended pads for any hopper you buy. I know we always build them to spec. Usually it's a reinforced concrete ring, 14-24" thick (depending on bin size) with a thinner (maybe 6-10") part across the center under the bin. There are even specs available on the soil if I recall. You can get your soil tested with a special probe (can't remember what it's called) that you push into the soil to measure how it resists push. We actually bought a little pocket version. You can calculate soil loading just by taking the estimated weight over the area of a ring beneath the support legs (which is given in the foundation specs).

For example, 10,000 bu of wheat plus a wild estimate for the bin itself comes out to about maybe 603,000 lbs. With a 24' diameter (not sure what our diameters were), we could estimate a ring that's 4' wide which is approximately 150 square feet, which is a ground pressure then of about 27 psi under the ring itself. Gravel spreads that load out as well. But gives you an idea anyway.

Yes with a flat bottom bin of the same size the load would be a mere 9 psi.

If a hopper falls over, it could be due to improper soil under part of the cement, or it could be due to an improperly built cement pad.

We recently build two 10,000 bu hoppers. Soil engineers recommended we remove a few feet of soil that was soggy and unable to support the weight, place a piece of special construction cloth (not expensive), then built it back up with compacted river gravel pit run. If I recall correctly, on that we built a pad that was about 24" thick for the ring, and 10" thick across the center part. Rebar throughout of course, a grid across the center. We built them round because it saves significant money over a big square pad. A local contractor did the rebar, forms, and pouring.

We have several 5000 bu hoppers that are in big steel ring skids, and they are sitting only on gravel. They are slowly sinking, but they are stable and aren't tipping. We tied them down with anchors screwed into the ground.
 
#5 ·
I wouldn't dream of putting a hopper on anything but cement. We have 12000 bu hoppers with skids on a concrete pad. Pad is 21" thick with two layers of re bar, 30 MPa. Bins are secured to cement with 5/8 × 6" concrete anchors at every leg.
 
#10 ·
That's weird. We got engineering foundation specs for each hopper we bought, complete with diagrams showing rebar spacing. Can't remember who they came from, but we bought them through Viterra at the time. I'll have to ask my dad where the foundation plans came from... maybe they didn't come from the manufacturer.
 
#14 ·
I have poured 14 21ft pads for 18ft 5000bus hopper bins over a 10 year period on are farm and these are some of the things I have started doing over the course of that time.

Cement 14inch thick for the 3ft than 6inches in the middle.
Outside 3 ft 4 rows of 15mm rebar. 2 high 2 low.
Across the whole pad 10mm rebar on 12inch centres

The centre ring 4inches of sand (unpacked) and 4 inches of geoform (which is basically styrofoam). The idea behind the geoform is that the outside of the pad has all the weight so when the cement pad sinks into the ground and the centre can give alittle against the geoform.
The pads will still crack at some point but it won't push up in the middle like it would if you packed the centre
 
#15 ·
Sounds like it depends a lot on the area what you need, but for us we peeled the topsoil off the top down to the undisturbed clay layer (which for us isnt really that far....), and then brought in some mix of coarse gravel and sand and spread it out on top and leveled it.. This has worked very well, with no bins leaning or sagging unevenly. The bins have sunk about 6" into the gravel, so now the skids are actually almost covered. This is for 12,500 to 17,000 bu hoppers.
 
#16 ·
I am about to build 2 10300bu hoppers and am a little uneasy about the base. They only recommend 12 inches of packed gravel on top of clay. We have recently built the level of our yard up by hauling in approximately 6000 yards of clay. Where the bins are going the level has been raised 4 ft from before I hope we have it packed enough. However one thing the bin guy told me was that the 2406 bins I am building have a triple 6X4 skid (some hopper makes use double 6X4 or triple 4X4) and he says this puts less PSI than a 1805 bin on double 4X4 skid due to the extra skid area. I also don't trust the anchors our neighbours have lost 3 bins in two years so I plan to use those concrete lego bricks to hold bin down also. I will defiantly be watching these bins closely also concrete is $290/yard in our area thanks to the potash mine expansion
 
#17 ·
$290 a yard. That sure seems high. What strength is that? Anything else added in it? 6000psi cement with hardener in it was around $150-160 a yard two years ago. I can see the new head frame at the potash mine from our yard.
 
#19 ·
In 2004 I set up a 21' dia. 8600 bu hopper on screw pilings and have been happy with the quick easy installation and nothing has moved. The recommended pilings were 14 [one under each bin leg] 4 1/2" x 5/16 or 3/8 wall pipe 5 meters long [16.4'] . The screw or helix is 18" diameter. It took the truck about 4 hours start to finish to install them all levelled and ready to weld a pad on the top of the piling to bolt the bin leg to. The driver laughed at the size of pilings I had been sold and said that was oilfield spec, about 10X overkill. Even at that it cost about $7,000 so maybe downsized a bit would be more affordable. When the truck is screwing the pilings in, they have a pressure gauge that tells them how solid the ground is and what the load capacity is. These pilings can be removed and reused if you want. Just thinking about the cost of a concrete pad or ring at $250 a yard plus steel plus labor maybe the screw piles would be a simple option. Might even get a bit of a break now that the patch is slow! I poured a thin 4" skin of concrete under the bin to make cleanup easier. Just a suggestion. Good luck.
 
#21 ·
How are you guys using skids anchoring them down? Clearly not everyone is because I saw more than a few tipped over hopper bins when I went out to Regina in June.

Transaxial those screw piles sound really good. Do you have stones? I have considered using those if I ever build a larger shop but I do have some stones.
 
#22 ·
We do have a few up to 8"? when you are dealing with a 16' depth. Very few big ones. We had no trouble with stones but I can see where it may be an issue. The installer did not seem concerned about rocks when I first talked about the job but maybe they kind of know the soil in different areas.
 
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