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

Reducing pile risk in liquefaction zone

Reducing pile risk in liquefaction zone

Reducing pile risk in liquefaction zone

I'm designing a foundation for a monopole structure out in a farmer's field. There is a big layer of sand that the soil report identifies as a potential liquefaction zone. The zone starts around 10 ft below grade and continues to 35 ft below grade.

I've designed a single pile extended to competent bearing material (about 45 ft below grade) as recommended by the soil report and DCPT tests. Checked the design for lateral pressures and deflection at-grade. However, I would like to present the client with an option to mitigate the seismic induced liquefaction risk.

Is there a way to make a foundation like this more "seismic proof"? It's too heavy to have a shallow footing supported by batter piles (for the lateral). The footing footprint ends up blowing up. A coworker was talking about vertical drains to dissipate the pore pressure, which I thought was an interesting possibility. But I'm wondering how possible (constructable) that would be?

I'm posting this to see if anyone has suggestions to steer toward or away from.

RE: Reducing pile risk in liquefaction zone

If it's sands then you can use ground improvement to increase the shear strength. DDC, VPC, rammed aggregate piers, ect. Probably not economically worth it though unless you have lot of structures to mitigate and they're relatively close to each other. I would assume just installing the pile deeper would be more cost efficient.

RE: Reducing pile risk in liquefaction zone

You seem to have given the best option with monopile to a non liq layer.

An alternative is ground improvement with shallow foundations, is your estimation of footprint size based on existing ground or improved ground? Cause that will obvs be less.

RE: Reducing pile risk in liquefaction zone

is it a reasonable claim that the sand layer would liquefy? Is the area prone to some typical earthquake? Is this for code?

The only soils that will liquefy are saturated granular soils with native void ratios greater than the critical void ratio. Then there's the anticipated design earthquake.

if you have blow counts and soil information you can look at the nomographs of Seed and Idriss to look at it for yourself. Then again, there may be codes?


ípapß gordo ainÆt no madre flaca!

RE: Reducing pile risk in liquefaction zone

Looks like the soils report recommended designing for liquefaction. For liability reasons, I wouldn't go against their recommendations to save the client a buck even if there was a low chance of happening.

RE: Reducing pile risk in liquefaction zone

Yeah. The soils report provided the liquefaction insight. Loose to compact sand. Site Class F (NBCC).

Thanks for the insight.

RE: Reducing pile risk in liquefaction zone

Do not use vertical drains alone for liquefaction mitigation.

You may consider ground improvement in lieu of piles (not piles plus ground improvement).
If you don't need uplift (net tension) for the foundation, then aggregate-based piers like vibro-stone columns or impact piers (previously proprietary via Geopier) are good alternates that provide both liquefaction mitigation and also increased bearing strength / reduced settlement potential.
Or deep dynamic compaction. Or RIC. Lots of ground improvement to choose from that does not involve concrete.

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! Already a Member? Login


Research Report - How Engineers are Using Remote Access
Remote access enables engineers to work from anywhere provided they have an internet connection. We surveyed our audience of engineers, designers and product managers to learn how they use remote access within their organizations. We wanted to know which industries have adopted remote access, which software they are using, and what features matter most. Download Now
eBook - Managing the Context of Product Complexity Using the Digital Twin
Keeping track of changes to complex products is difficult—think Aerospace & Defense equipment, new generations of commercial aircraft, and software-based automobiles. A new way to managing the digital context of the physical product is required and the answer is the Digital Twin. This ebook explores the opportunity available for Operations and Maintenance for the Digital Twin. Download Now
White Paper - Trends in Industrial Filtration
Substantial progress has been made in filtration technologies in recent years. New filter media materials, designs and processes have led to filters that are more efficient, reliable, compact and longer lasting. This white paper will discuss the various trends that are impacting operational responsibilities of MROs today and the resources that are available for staying up-to-date on the latest filtration solutions. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close