×
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

H Pile Driving into Shale

H Pile Driving into Shale

H Pile Driving into Shale

(OP)
I'm working on a site that has used 12 x 53 steel H piles for end bearing piles. I'd like to use these piles again (Grade 50), but I also need the pile for lateral capacity purposes. I'd like to embed the pile a minimum of 1 ft into a shale grading highly to moderately weathered, +/- 5,000 psi unconfined strength. I need this embedment because the soils above the rock are pretty crappy. I'm planning to use pile points, and I'll be specifying a wave equation analysis prior to the start of work for the Contractor.

I was thinking of writing the spec so that it gives a minimum penetration requirement into the shale, and let the contractor figure out how to do it. Maybe, require the Contractor to submit a pile driving plan with contingencies should they be unable to get 1 foot of penetration with an impact hammer.

Does anyone see any issues with this approach? Thank you for your time.

RE: H Pile Driving into Shale

jamoca67 - I don't believe that 12 x 53 HP, even with pile points, can withstand impact driving needed to do accomplish that 12" penetration... but that is just my opinion. Could drive a few index piling before bidding the contract, or shortly after contract award? This would give you a definite answer. Is the 12" penetration a required number or a goal?

www.SlideRuleEra.net idea
www.VacuumTubeEra.net r2d2

RE: H Pile Driving into Shale

Does your lateral capacity requirement mean a "toe hold"? On what basis is this figured? Using bedding plane shear strength? How would you test that capability if you had to?

RE: H Pile Driving into Shale

A Google search for "rock socket design" comes up with plenty of info. Do these fit with your design method?

RE: H Pile Driving into Shale

5,000 psi is still pretty good shale. Consider that it is stronger than typical concrete (3-4 ksi). The problem you will run into is that a pile hammer big enough to drive the pile into this rock a significant distance will also be too big to drive the pile without damaging it. In order to put that much energy into the pile, you will end up exceeding the yield strength of the steel. If you really need that much of embedment, you will have to drill and socket the piles into the shale.
But what about using battered piles? Will this be able to provide your lateral resistance?

RE: H Pile Driving into Shale

The OP stated that the shale was grading heavily to moderately weathered. I find that statement at odds with an unconfined compressive strength of 5000 psi which is about 350 kg/cm2 (or 360 US t/ft2). As a quick check against unconfined compressive strengths for shales, Roy Hunt's Geotechnical Engineering Investigation Manual provides a range of 7 to 350 kg/cm2 for shales (Table 3.26). I would think that with a "standard" hammer (not too big) that you should be able to drive further than 1 ft into the shale - please check your unconfined compressive strength.

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