×
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

CPT Gauge Calibration

CPT Gauge Calibration

CPT Gauge Calibration

(OP)
What time intervals do most calibrate the guages for CPT (or Piezo-cone)? 6 months? 12 months?

RE: CPT Gauge Calibration

BigH

Interesting question . I looked into the technical brichure of Gouda and Van den Berg, they don't say anything about frequency of calibration. CPT test is covered by an ASTM standard ( I don't work with it ). I have an old 1979 version of ASTM D3441 where they don't even talk about calibration ( they call for +/- 5% accuracy ).
I would say it's important to carry out one calibration before using the machine ( some parts can be exchanged in 100 and 200 KN heads from Gouda for example and can lead to results 4 times greater than reality ! ). If your tests are carried out in soft soils, i don't believe you need another calibration except if you change parts in the head ( mechanical ) or change the electric cone. If you are working in ranges close to the maximum capacity of the rig, or in case the head or the cones have been hit, it would be necessary to check again.

RE: CPT Gauge Calibration

BigH:

If you're referring to calibration of the instruments, and not "zero readings" (or baseline readings) which should be performed before and after every sounding, actual calibration frequency should probably depend primarily on frequency of use, and care/maintenance by the operator.  I believe there is some guidance in the ASTM Standard (D 5778) as well as the International Reference Test Procedures (I believe established by ISSMGE TC16).  The SGI also authored a report specifically on CPTu calibration - I think it came out around 1990, but cannot recall the report number.

FYI, all, a great free reference on the CPT (SCPT, SCPTu, etc etc) is the NCHRP Synthesis 368, which can be found at:

http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_syn_368.pdf

Also, I just returned from the Second International Conference on the CPT (CPT '10 - http://www.cpt10.com/) and I understand that the organizers intend to fully publish the conference proceedings free on-line (eventually).  Watch for that...

And if you haven't checked out Paul Mayne's website, you're missing out on a wealth of free informations:
http://geosystems.ce.gatech.edu/Faculty/Mayne/Research/index.html
 

RE: CPT Gauge Calibration

(OP)
mdhshanwil - thanks for your comments; I went to uni with Paul.  I'm talkin the gauges - like we get our compression machine gauges calibrated once per year. I was thinking that the calibrations should be at a minimum every 6 months.  The drilling contractor that will be used by one of our contractors submitted calibrations that were nearly 3 years old - too old for me!

RE: CPT Gauge Calibration

From Guide to Cone Penetration Testing for Geotechnical Engineering by Robertson, it mentions that "Calibrations should be carried out at regular intervals (approximately every 3 months)".

However for the contractor,it is commonly 1.5 years.

RE: CPT Gauge Calibration

(OP)
Thanks pagenel.  Already told the contractor to tell his drilling sub "to take a hike" or get a new calibration.  I'd be happy if it was within 6 months; being in Indonesia.

RE: CPT Gauge Calibration

It is also depend on how frequently the mobilization of your Machine

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