How to auger a 18" hole through sand that's collapsing

[masscity]

We have to auger through 5' of compacted sand and into the virgin clay for the columns on a Pole Barn. Problem is the sand just keeps collapsing. Cleary Buildings is doing this.

Now trying to figure out how to do this. Someone from Cleary mentioned using a 20" sonotube around the auger, but they said it won't work. They said you can't push the tube down with the auger.

I think it would be worth giving it a try, but they don't want to. You guys got any ideas or and experience with using the tube around the auger?

Out of 35 columns, 11 are in deeper sand.

Thanks for any help you can give me.

Ed

 

[Illini22]

We used 35-50 gallon barrels when setting electri poles in loose gravel, sand. The barrel just keeps sinking into the hole.

 

[masscity]

We used 35-50 gallon barrels when setting electri poles in loose gravel, sand. The barrel just keeps sinking into the hole.

So you as you augered down the barrel dropped with the auger. You didn't have push it down at all?

 

[tcartwri]

Mix some bentonite into a slurry and add it to the hole as it's progressing. It should stick the walls together long enough to get the poles in.

 

[sailfast]

Yes, It will naturally drop down if it has any weight to it. Will need to auger out more material than usual but it will go right in.
Sonotube might be a little bit on the light side and need a little bit (10 pounds) of pressure to help it along.

 

[Lloyd_E]

How cold is it there now? Could you hose(mist spray) the hole/walls lightly as you go down? The moisture may keep the sand together and the temps may freeze the sand/walls in place until you get the tubes in.

 

[masscity]

I don't think they will want to mess with something like bentonite. It's not cold enough for serious freezing yet. Last winter was the first winter anybody remembers frost in the ground here.

We get snow before the ground freezes here. You can pick carrots out of the garden in the middle of winter if you want to shovel 3-4 feet of snow first.

The idea was to auger down, bringing the tube/barrel down with it, drop the cookie(concrete) to the bottom of the hole, put the column in, throw in two bags of sakrete, then pull the tube out, let it collapse and go to the next hole.

We have a highlift here with a 40' boom so we can get the tube over the top of the column.

Thanks for the ideas.

 

[tcartwri]

Bentonite is powdered clay... comes in 50lb bags. It's what they use to seal the casing on your water well.

 

[SPIKER]

I would think a large enough sonotube could be put in with the auger around it. If you can spot weld a larger flat plat to the auger to push down with they should go down together. Maybe use some beam clamps to clamp onto the auger flight, the beam clamp can have larger round plate welded to it. Would need to use some threaded rod on the beam clamps that the clamps thread thru. plate would look like a flat doughnut. it would need 3 threaded rods welded to it just long enough to get clamps onto the flights bent in if needed. as you auger it in the plate and sono tube slip the dirt comes out the top of the sono tube and the plate pushes down the sono tube as the bottom is augured out from under it.

Otherwise will need to excavate a large hole drop in a big concrete cookie at depth and add poles then back fill with good dirt/gravel/sand and tamp in 1 or so foot lifts of back fill to make sure the poles are tight.

Mark

 

[wroughtn_harv]

Old fenceman's trick is to wet down the sand, but his is for post holes. If it's the top of the hole that keeps collapsing I would try a larger size sonotube for the first couple of feet. I would wet it down a bit and then dig it on out.

It could be worse, the sand could be holding a layer of water above the clay.