×
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

Split-spoon sampling

Split-spoon sampling

Split-spoon sampling

(OP)
Hi, I'm trying to solve this problem but i can't...

the following table gives the variation of the field standard penetration number (N60) in a sand deposit (then there's a table)
if the groundwater table is located at a depth of 6m, dry unit weight of sand from 0-6m is 18kN/m^3 and saturated from 6-12m is 20.2kN/m^3, and D50 is 0.6mm, estimate the variation of the relative density with respect to depth.

depth (m)     N60
1.5                6
3.0                8
4.5                9
6.0                8
7.5                13
9.0                14
i know i have to use this equation:


Dr(%) = ([ N60(0.23+0.6/D50)^1.7)/9] [1/sigma prime knot/pa])^0.5 x (100)

My only question is that since there are multiple depths... how do i go about calculating it?

RE: Split-spoon sampling

In my view the N value related to other things is generally some person's idea of a correlation.  If they were out on the jobs, they would see that all sorts of things can affect the number even if the soil does not change.

I'd shy away from any formula with "precision" relationships.  It just ain't that good a "testing" system in my view.

RE: Split-spoon sampling

DM 7.1 or 7.2 has a graph showing the relative density as a function of blow counts.  I think they use N1-60 values.

What is the actual engineering problem that you're trying to address?  Is this for pile design, earht pressure, etc.?

I'm pretty sure that if you are normalizing blow counts for the purposed of determining relative density you have to adjust for 1 tsf of confining pressure.  Your OP doesn't address this however. . .

f-d

¡papá gordo ain't no madre flaca!

RE: Split-spoon sampling

"I'm pretty sure that if you are normalizing blow counts for the purposed of determining relative density you have to adjust for 1 tsf of confining pressure."

It looks like it does adjust for confining pressure. [1/sigma prime knot/pa])^0.5 looks just like Cn for liquefaction assessment, since pa is almost exactly 1 tsf.

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