Cleaning holes for end-bearing piles

[piutehowie]

My structural guy is concerned about cleaning out residual debris from the drilled holes for end bearing piles of 24 in dia. Does anyone know of a device/method for cleaning out the last of the spoils from holes too small for a person to fit down??
Thanks
Howie

 

[worldofmud]

Most of the specialist piling contractors will use a 'clean out' bucket, basically a bucket with a hinged base which is rotated in the bottom of the hole and loose material is collected. This seems to be the accepted method as H&S frown on the man down a hole approach, although this may depend in which country you are in.

 

[BigH]

worldofmud - correct - but 24 inch dia would be too small to send someone down anyway - we wouldn't do unless 36 inch dia. We are assuming, too, that he is talking about bored or drilled shafts, eh?

 

[piutehowie]

Thanks for the help. The problem is that the spec was for end bearing (yes, bored) piles and the structural wanted a spec for friction but the soils report is already approved. The friction piles would be longer at this dia so there is a cost issue as well.
Thanks
again
Howie

 

[Speedycrete]

A vacuum truck?

 

[BigHarvey]

If your pile is drilled under bentonite, the normal procedure is to desand the mud with a pump lowered at the bottom of the pile and then before lowering the reinforcement, clean out again with a bucket in case some materials would have collapsed from the walls.
If end bearing is that essential for your project then install grouting pipes in the reinforcement and grout the point of your pile.

 

[SmokeyBear]

worldofmud correct.Provided accurate depth of drilling is measured, so you know where you actually drilled to, a good clean-out bucket can remove all but a handfull of spoil. You can visually check base cleanliness using a torch. In other than rock, you can actually "drill" a little with the clean-out bucket to ensure base clean out.
In OZ, Workplace Health and Safety would emasculate anyone even thinking of going down a drilled pile hole; unless, confined space ticket held, trained observers, resue equipment ready etc etc.
Unfortunately there is a practice known as "chucking some water down and spinning the auger" used by some.

 

[hokie66]

If the sun is shining, best way to see the bottom of the hole is to use a mirror. "Ol Sol" gives a much better light than a torch, or flashlight for those in the US.

 

[worldofmud]

All of the above replies assume that piutehowie is dealing with a specialist piling contractor. Is he/she? If not the replies require re-assessment. piutehowie?

 

[worldofmud]

let me rephrase that to 'some of the repies' (mine included)

 

[oldestguy]

Use a magnifying mirror, like for putting on make-up. Works great.

Also, hang a heavy rod on a light rope and watch what it does.

You may have to go to some form of compaction. I never trust machines alone doing the job.

 

[BigH]

The mirror routine or flashlight routine works well if a tad of water at bottom (for better reflection - a tad, not litres) - but not sure it would be good for the 75 m bored cassions like you see in Bangkok! For many of those piles, they weld a flat plate on the end of the rebar cage that is dropped in the hole. Attached to the underside is a rubber bladder with a couple of tubes running out of it through the plate to the surface. After installation, and the shaft concrete has set, they would pressure-grout the base (i.e., fill up the rubber bladder). this would compress the "loose" sand that is typically found at the bottom. How I saw it done at least.

 

[Mccoy]

BigH,
by your description I recognize, with some modifications, the "flat-jack" technique some contractors use in Italy. I've always believed it's a great way to ensure the pile's end does not lay upon sh..oot