×
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

Horizontal Modulus of Subgrade Reaction

Horizontal Modulus of Subgrade Reaction

Horizontal Modulus of Subgrade Reaction

(OP)
I'm working on a problem where a retaining wall will be loaded toward the backfill, and I'm trying to come up with some deflections. I've created a model of this structure with a mesh of spring supports to simulate the backfill. I'm looking at the Das text Principles of Foundation Engineering, chapter 11 section 16, for horizontal modulus of subgrade reaction. This whole section is about piles, but I'm wondering about applying his Nh values (in pci) toward my spring mesh. Basically, K (lb/in) = Nh (pci) * depth of spring (in) * tributary width of spring (in).

RE: Horizontal Modulus of Subgrade Reaction

A rare circumstance. I'd just use the usual geotechnical methods evaluating lateral earth pressure, active and in this case passive.

RE: Horizontal Modulus of Subgrade Reaction

to my knowledge, retaining walls are not designed using horizontal modulus that is intended to be applied to piles. A pile is anywhere between 0.3m to 2.8m+ in diameter. Retaining walls are typically designed using Plane Strain methodology. There is a strain incompatibility issue.

I do know that WALLAP using a subgrade reaction model, but i doubt it is the same methodology as piles.

RE: Horizontal Modulus of Subgrade Reaction

movement to mobilize passive pressure is about 3x the movement to mobilize active pressure.

Does that help?

f-d

ípapß gordo ainÆt no madre flaca!

RE: Horizontal Modulus of Subgrade Reaction

(OP)
Thanks y'all.

fatdad, so say I have a 20' cantilever wall.

1) Is this movement measured at the same location of the developing pressures? E.g. Let's say it's 1"/10' to develop passive pressures. At 15' up the wall, I'll need 1.5" of deflection towards the backfill at that location for passive pressures to develop? What about at the very bottom of the wall (z=0)? I theoretically need 0" of deflection for passives? Or is it that the top of the wall needs to maximize deflection (2" in this example) before passive pressures can be considered anywhere?

2) In my particular case, where I'm designing for a loading scenario towards the backfill, I will never have active pressures. Active pressures only develop when a wall moves away from the soil, not towards. So unless I'm willing to allow the passive deflections, I should use at-rest pressures?

3) If I model this thing with at-rest pressures return deflection values in excess of the 1"/10' rule, that means my model is no good and I need to reiterate using passive pressures? Conversely, that model using passive pressures should show at least 1"/10' deflections to be considered valid, right?

4) I don't think I really have a cantilever wall - It's a got a significant curvature to it, which going to stiffen it up and make it act in some ways like a braced wall. Now, for purposes of analysis, if I can prove the wall without counting on this self-stiffness, all good! But is there anything additional I should keep in mind in this situation, from a geotech perspective, as opposed to a typical flat cantilever retaining wall?

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


Resources

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