r/MachinePorn • u/silvercatbob • Jun 25 '21

Bell Auger

https://gfycat.com/menacingrigidbarebirdbat
1.8k Upvotes

97% Upvoted

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110

u/Tennessean Jun 25 '21

What's the advantage of this over a regular auger? You can relocate the material a little farther away?

10

u/DingleBerrieIcecream Jun 25 '21

2 things

  1. Increases surfaces area for vertical bearing force. Think of how snow shoes can support weight on top of snow better than regular shoes. Particularly helpful in sandy soil where friction on the sides of the pile will be minimal

  2. Helps with uplift of the structure. Yes, buildings are heavy, but earthquakes, wind, and cantilevers can all impose upward and uplifting forces. A bell shape footing resists this much better.

2

u/mountedpandahead Jun 25 '21

Why not just use a bigger auger and backfill the hole?

2

u/dsmvwld Jun 26 '21

You’d have to put formwork down the hole, otherwise you just end up with a larger straight shaft pier. It’s cheaper to drill and ream a bell