×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Cleaning Belled Piers

Cleaning Belled Piers

Cleaning Belled Piers

(OP)
How are the bells in belled piers cleaned out? I saw a patent for a belling tool that collects and removes the dirt as it drills. Is this typical? Or is the loose dirt removed by hand? (people and buckets?) I'm new to belled piers and want to learn what the typical practice is. ponder

RE: Cleaning Belled Piers

Nobody likes to go down there. However, for a belled caisson, I'd never do it. There is a good chance for the sides to cave in on the "inspector". So, we try to examine the bottom from the surface. One excuse I have heard (and have had to accept) is assume that a certain percentage of the bottom is a pile of loose earth that the cleaning tool can't get. My experience is limited to perhaps 10 jobs, so those that have more experience may come up with a good way to approve what is done before concreting. I usually would be the first to go down (inside a casing) to set the procedure for the production inspector. Of course all sorts of safety procedures are needed in case of CO2 and of course passing out. Hand clearing is the best, but there are some contractors that do not do that.

The best person to learn from is Clyde Baker who wrote this manual:

http://www.browntechnical.org/products/Drilled-Sha...

RE: Cleaning Belled Piers

We usually rely on the belled tool that the drillers use. I don't believe that OSHA lets workers into shafts unless they are cased.
The leftover scrap soil at the bottom gets "tamped" by the weight of the wet concrete eventually to some extent.


RE: Cleaning Belled Piers

As previous posts say, inspection of belled piles (also called under-reamed piles in UK) is carried out from surface now. A couple of companies over here have developed specific tools to visually inspect the base of the pile using a camera. One also allows you to recover U100 samples from the base so any softening can be seen. See http://www.nce.co.uk/less-is-more/541244.article

RE: Cleaning Belled Piers

One of my first jobs was a large belled caisson in Southern Ontario - in tills - so they stood up with no problem. The shaft was cased. We used to spend time there as it was really cold up on top! Times have changed.

RE: Cleaning Belled Piers

On a sunny day, I use a mirror to reflect the sun's rays to the bottom of the hole. Much better than any type of artificial light.

RE: Cleaning Belled Piers

I thought that a video camera and lights were used to avoid sending someone into a grave.

RE: Cleaning Belled Piers

I have inspected numorous belled piers over the last 25 years, never felt the least bit of concern for my safety. As others have pointed out, current US rules make it difficult but not impossible to peform downhole inspections/cleaning. Nothing beats a laborer using a shovel and bucket to clean the bottom of a shaft, belled or straight. When I prepare foundation recommendations, I provide two options. One with hand cleaning and one for machined cleaned. Needless to say the hand cleaned shafts get a higher allowable pressure.

On a side note, the largest bell I every inspected was 12.5 feet off a 6 foot shaft in shale.

Mike Lambert

RE: Cleaning Belled Piers

Mike - mine was 15 ft bells - about 15 to 20 ft down in good Southern Ontario Glacial Till. We found that after cleaning, within several minutes, the upper couple of inches would "soften". As a result, we would clean and get out and place the concrete with some speed.

RE: Cleaning Belled Piers

BigH - 15 feet is impressive! We didn't have any issues with these in the shale. Good material no significant water inflow, you and half-a-dozen of your closest friends could have lunch in these things. Biggest problem was not going too deep into the unit as the target material was underlain by a poorer shale. If you missed the target the shafts would have to extend to limestone bedrock another 40 feet or so down.

Mike Lambert

RE: Cleaning Belled Piers

One tip I learned a while back. For the mirror and sun technique, use the mirror your wife used for magnifying her make-up. It sheds a strong light with some width. I find it is helpful for the guy down there also.

RE: Cleaning Belled Piers

i use a RIGID color see-snake. i tie it to a long rebar with a 90 bend at the head to control it

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources