×
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

Correlations between CBR and PI

Correlations between CBR and PI

Correlations between CBR and PI

(OP)
Correlations between CBR and PI has been found from dynamic cone penetration test with 17.6lb hammer and 22.6in drop height. Are these correlations valid for portable dynamic cone penetrometer with 15lb hammer and 20in drop? If not, is there any way to estimate CBR from the test result of portable dynamic cone penetration test?

Thanks,
Sonia Shahnaj
Berkeley County Gov., SC

RE: Correlations between CBR and PI

We usually estimate CBR using soil classification (particle size and Atterberg limits) data, usually by Group Index. Yes, it's kind of crude, but at low CBRs (fine-grained soils), it usually doesn't make much difference to a slab or pavement design.

Otherwise, grab a sample and perform the Proctor and CBR testing needed to generate the "real" CBR of the subgrade. It'll waste less time than arguing over empirical relations.

Jeff

RE: Correlations between CBR and PI

I agree with Jeff...if the expected value is going to make a difference in your design, test it.  If not, "guess" it from classification data.


Jeff...I'm expecting some info from BigH that I'll pass on to you.

Ron

RE: Correlations between CBR and PI

For a couple hundred bucks you can just do a CBR test - that's what I'd recommend.  I have found MH soils with CBR values of 14 and SC soils with CBR values of 3.  The consequence of failure (premature design life) are too great to just guess - unless you just guess a value of 3.  Also, there are pretty good correlations between CBR and subgrade modulus so from the CBR test you can help the structural designer with a site-specific modulus value!

Good luck.

f-d

¡papá gordo ain’t no madre flaca!

RE: Correlations between CBR and PI

fattdad (Geotechnical) Feb 12, 2007
For a couple hundred bucks you can just do a CBR test - that's what I'd recommend.  I have found MH soils with CBR values of 14 and SC soils with CBR values of 3.  The consequence of failure (premature design life) are too great to just guess - unless you just guess a value of 3.  Also, there are pretty good correlations between CBR and subgrade modulus so from the CBR test you can help the structural designer with a site-specific modulus value!

Good luck.

f-d

 

¡papá gordo ain’t no madre flaca!

RE: Correlations between CBR and PI

Ron,

FYI, my personal address is jtdonvilleAThotmailDAWTcom , in case you need it.

"Do the needful" with the uppercase letters.

Jeff

RE: Correlations between CBR and PI

jdonville - am still trying to get the CD to you. cheers

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