×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

Soil sub-grade modulus
3

Soil sub-grade modulus

Soil sub-grade modulus

(OP)
Dears,
I want to know the correct way to calculate the Soil sub-grade modulus, is the correct value is Kv = P/D where P is the allowable pressure and D is the corresponding allowable settlement or P is the ultimate pressure and D is the corresponding ultimate settlement?
Since i found in many soil reports that the Kv= FS*(B.C)/D where D is the allowable settlement

thank you

RE: Soil sub-grade modulus

I use this graph to get a general understanding of K values (I use the K(30))
We would use this in a service level basis (not factored or ultimate loads).



Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies

RE: Soil sub-grade modulus

JAE's post is on point. But if you need a quick back-of-the-envelope type of calculation, which doesn't apply to rock or soils with cobbles, Bowles made an approximation in 1974 or something: Ks = 12(SF)qa k/ft3. Source: his textbook, but this article too: https://www.structuremag.org/?p=1239.

RE: Soil sub-grade modulus

As an aside, how do you guys estimate an allowable bearing from a CBR? I used to have a handy little chart but lost it along the way!

RE: Soil sub-grade modulus

I wouldn’t use CBR to allowable bearing pressure. One because I don’t consider it realiable and two because it would only be allowable based on shear failure. Settlement typically controls allowable bearing pressure.

RE: Soil sub-grade modulus

JAE: what is the source of the figure you provided? I have a reference that includes a very similar figure but it is not identical to the one you posted.

RE: Soil sub-grade modulus

Thanks Eirechch. Good to know. I think the graph I had years ago started with a known CBR value, would then approximate a subgrade modulus and from there would estimate approx allowable bearing. Can’t remember where or how I even got it!

RE: Soil sub-grade modulus

Hokie93 - I've been asked that several times - got it from an older engineer back years ago - think it is from some textbook.

Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies

RE: Soil sub-grade modulus

JAE: In case you are interested, the figure appears to be taken from ACI 360R-92 (Design of Slabs on Grade), or an earlier edition. It is Figure 3.3.5 in ACI 360R-92. The original source is cited as a 1986 paper by B.C. Ringo ("Design and Construction of Concrete Slabs on Grade"), ACI SCM-11(86). The figure has been revised in ACI 360R-10.

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

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. 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