helical screw piles
helical screw piles
(OP)
I submitted this post a couple of years ago, but I thought useful to post it again.. We did receive several thoughtful replies. But at that time many engineers had a few questions about them themselves, having used them very little and were a little skeptical. The post read as follows: “ Who can tell us the present status of industry acceptance of helical screw piles as a deep foundation system for small (or large) commercial buildings (wood or steel) as well as acceptable design procedures for vertical and lateral loads"
Thank you
j
Thank you
j






RE: helical screw piles
Side note: He also said that helicals will get plastic deformation at their soil-concrete interface and that can act like a dampener in a seismic condition (not sure about this one!)
Anyways, I think they can successfully used for full structure support similar in fashion to any other more historical driven system. I think building codes even have special inspection procedures in relation to helical installation now.
RE: helical screw piles
I live in an area with a lot of plastic clays so they get installed pretty regularly on older homes.
RE: helical screw piles
http://www.abchance.com/resources/technical-litera...
EIT
www.HowToEngineer.com
RE: helical screw piles
The biggest mistake I see with their use is a contractor learning how to do them and then coming in and wanting to install them everywhere. In areas where qualified or affordable field labor is an issue, contractors can latch onto these as an affordable alternative to deep foundations. BUT, they MUST be installed in the right soil which can only be determined with extensive geotech analysis.
Great system if it's the right application.
PE, SE
Eastern United States
"If a builder builds a house for someone, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death!"
~Code of Hammurabi
RE: helical screw piles
If the contractor doesn't drive far enough it is their responsibility to fix it once it fails. So i am not sure if i am too concerned with them cheating the system. Most contractors have a 20-lifetime warranty on their helicals
RE: helical screw piles
Dik
RE: helical screw piles
Dik
RE: helical screw piles
For us, the cost was about the same for deep foundations and slightly higher for shallow piers. But the schedule was a big benefit, so that was enough for the client. An additional benefit was that when you have a lot of excavation for site grading, the PVR is not as much of a factor for helicals as concrete piles. So, again a big benefit.
I'm not sure what you're looking for as far as "industry acceptance". I don't know if you can get much better than having them accepted by the IBC.
RE: helical screw piles
RE: helical screw piles
Dik
RE: helical screw piles
RE: helical screw piles
Unless battered I wouldn't think of using them for lateral loads.
RE: helical screw piles
Ditto to everyone who said it is all about installation into the right soil strata. I think it helps to have at least one SPT to know what you have before you get into it. We have had issues with stiff clay as they get very high torque values and the contractor will want to stop, but if they terminate in active plastic clay that can make the problem even worse (we have worked with failed helical piers that act like a piston in active clays).
I think they would make great uplift anchors for high wind areas and applications with little dead load like pre-engineered steel buildings. Instead of using massive concrete blocks, you could use a small pile cap/foundation and then get the uplift and gravity load capacity from the helical.
RE: helical screw piles
RE: helical screw piles
http://www.amazon.com/Helical-Piles-Practical-Desi...
EIT
www.HowToEngineer.com