Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations SSS148 on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Two questions on helical anchors, from Chance ICC report

Status
Not open for further replies.

AaronMcD

Structural
Aug 20, 2010
273
Chance_ICC_lgytoo.jpg


I'm confused by this section. I'm told they install these all the time using torque correlation only, but this paragraph appears to require either calculations based on a geotech report or load tests. Is it permitted to EVER use torque correlation only? I'm working on a house with a site retaining wall, 7'-14' from base of foundation to finished grade. The contractor wants to use helical anchors to reduce the excavation - there is nowhere on the sloped site to put all that soil. They do not want to do load tests or new geotech borings in the vicinity. The geotech thinks the soil is good and there's no need for additional borings or load tests. They have done a few probe piles.

Secondly, the last sentence appears to make no sense to me. The way I read it, it is requiring all anchors to fail (installation torque correlation exceeding calculated or tested capacity). What is it really meaning to say?

Thanks.

 
Replies continue below

Recommended for you

Perhaps what it is meaning to say is that the installation must verify the calculation or test, and it is not permitted to install to a lower torque correlation value than calculated or tested.

 
I'm not sure what code you screenshotted above, but in the IBC it states "Helical piles shall be installed to specified embedment depth and torsional resistance criteria as determined by a registered design professional. The torque applied during installation shall not exceed the maximum allowable installation torque of the helical pile."

Very rarely do I ever see anything, but torque used to determine helical capacities. Typically only if we have large uplift loads or if the piles will be extended above grade does a further analysis happen around here.

 
That's from an ESR, not the code itself. And it makes sense. Some areas have pretty uniform soil or the soil gets better as you go deeper. In those areas, you're probably safe with torque for lightly loaded applications. Around here, not so much. I've seen soil reports with good/decent soil overlaying muck, lenses of stiff or soft material, even obstructions 20' below grade in some of the old, 'reclaimed' areas. Any of these could completely invalidate the torque to bearing strength correlation. Because that's all it is: a correlation.
 
Around here for new construction or big renos/additions, borings are basically required so we already get the soil profile and estimated capacites. For smaller stuff or repairs most times not.
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor