Helical Pier Capacity
Helical Pier Capacity
(OP)
Hello all, I would like to get an opinion on the use of Helical piers . We have soft soils over bedrock to a depth of +/- 30'. Soils report recommends caissons. Contractor has suggested Helical piers due to depth to ground water(10') since he says the cost to case the holes are significant. Geotech approved the use of helicals and requires helicals to be "seated" in bedrock. Column loads can range in the 300-600 kip range, so multiple helix will be required. My question is, how do you "seat" the helix in bedrock.





RE: Helical Pier Capacity
RE: Helical Pier Capacity
RE: Helical Pier Capacity
I used these helical screw pile on a job about 8 years ago - a large premanuf metal building on fill with a structural slab. Had problems with pile breaking off as they were screwed into place, and with the tips hitting large boulders necessitating relocation - typical in any pile job I guess.
Also had a problem with the contractor as he was the only one in the area with the special equipment and license to do the job. $$$$$$$$ Just a thought if the equipment breaks down, as it did. But the project did get completed and the building is holding up just fine.
Mike McCann
McCann Engineering
RE: Helical Pier Capacity
RE: Helical Pier Capacity
RE: Helical Pier Capacity
RE: Helical Pier Capacity
To confirm my point, check out the following article, particularly under disadvantages.
http:/
csd
RE: Helical Pier Capacity
I would not use helical piles for end bearing. Matter of fact, I'm not sure I'd use helical piles for column loads of 150 to 300 tons. Maybe I'm just old fashioned. . . . .?
f-d
¡papá gordo ain’t no madre flaca!
RE: Helical Pier Capacity
csd
RE: Helical Pier Capacity
RE: Helical Pier Capacity
RE: Helical Pier Capacity
RE: Helical Pier Capacity
Second "amen".
f-d
¡papá gordo ain’t no madre flaca!
RE: Helical Pier Capacity
RE: Helical Pier Capacity
RE: Helical Pier Capacity
RE: Helical Pier Capacity
RE: Helical Pier Capacity
RE: Helical Pier Capacity
RE: Helical Pier Capacity
Augercast piles are bored using a hollow continuous-flight auger. As the auger is withdrawn, grout is placed under pressure from the auger tip. Any steel is placed after the auger has been completely withdrawn.
lsmfse,
It sounds to me like one of these two methods would be much more appropriate than a helical pile. Helical piles develop their capacity from the helices bearing on the soil, not in end-bearing. The Contractor in this instance is not giving you good advice.
Jeff
RE: Helical Pier Capacity
Seating the screw piles into rock is not new. The pile will not 'spin' just short of the bedrock because it is the helix that advances the pile, not the tip. Besides, there's a higher pressure under the tip which can cut into the rock until the helix reaches it - this is called seating.
Having said that, make sure the pile design does actually have a 'tip' per se and not just a tube cut at 45 degrees. A cut tube will not penetrate the rock.
RE: Helical Pier Capacity
http://st
RE: Helical Pier Capacity
50 tons is readily achiavable with a mini pile and higher capacities have been achived. A down the hole hammer allows seating into most rock. A newer twist is mini cassions that are somewhat larger in diameter and have a small cage as opposed to a central bar.
RE: Helical Pier Capacity