PIT - Pile Integrity Testing - Requirements?

[Armar007]

I have about 300 Auger Cast Piles going in a refinery. PIP STS02465 Section 5.2.1 States that --
"Piles shall be tested as specified in ASTM D5882 or by single or cross hole logging as specified in ASTM D6760 or both, as specified in the contract document."
The question is do we have to test each and every pile or just the piles for which we suspect a problem due to discrepancies in the data (actual amount of grout much less than the estimated etc)? What is the normal practice?

 

[Ron]

Test at least 10 percent of the production piles. If you find a failure rate higher than about 5 percent, test more.

 

[massagung]

the normal practice in my regional about 10% of ammount piles, which that tested pile have discrepancy data or potential defect (such us necking or others), usually we compare the drilling/piling record and then we define the tested pile for PIT.

M.A.

 

[QAMaster]

I'll agree that 10% sounds reasonible, but the bottom line is it should be in the specifications. If they are going to tell you that this testing has to be done, then they should also be telling you how often.

Typically, the piling contractor performs an index pile program, by selecting pile locations across the site to install and record data prior to production work. The test piles are then selected from the index pile program, usually the worst case situations and the average conditions. The engineer may require additional testing during the production piles if there are any that are suspect, due to low grout takes or abnormal installation conditions.

I do not favor D5882, due to variations of the surface conditions of the piles. D6760 is a good test, but is highly dependant on the installation of the access tubes and the timing of the testing.

We have DOT projects that require every drilled pile undergo integrity testing, so again I believe the quantity/frequency should be specified by the engineer. These tests are the oldest typically performed, and can be relatively time consuming. There are newer and more reliable methods of determining the integrity of drilled piles. You may want to look at the GRL/PDI website, they practically invented pile integrity testing. They have equipment that will provide similar information by monitoring and recording the integrity of each pile as it is installed, without causing any loss in production time.

 

[Armar007]

Thank you all.
Here is what I found in “GEOTECHNICAL ENGINEERING CIRCULAR (GEC) No. 8 - DESIGN AND CONSTRUCTION OF CONTINUOUS FLIGHT AUGER PILES – FINAL - April 2007” by FHWA.

7.5.1 Use of Integrity Testing
Integrity test methods require careful interpretation, which should be performed by experienced
personnel. However, integrity testing personnel cannot always determine whether an anomalous
reading is a defect within the pile; therefore, the final decision on acceptability of the pile must
be made by the design engineer based on the site specific soil conditions, construction records,
the post-installation integrity testing report, and analysis of the possible effect on foundation
performance.
As discussed previously, the most reliable means of achieving consistent QA/QC is automated
monitoring and control during construction, with documentation of the installation via these
measurements. The use of post-construction integrity testing is best utilized to verify that the
installation parameters used for control (i.e., penetration speed, grout or concrete pressures and
volumes during auger withdrawal) are appropriate for the site-specific project conditions.
Integrity tests can also be used to further evaluate piles that did not meet drilling or grouting
criteria. Coring of the piles can be used to supplement or to provide a visual check of suspected
defects detected by integrity testing.
[highlight #FCE94F]The necessary frequency of post-construction integrity testing is left to the judgment of the
owner and can vary from project to project. A frequency of 10% to 20% of production piles
subjected to integrity testing is typical. In addition, all preproduction and verification test piles
should be tested. When agencies have little experience with CFA piles, particularly difficult
project conditions exist, or project or site conditions give reason to expect problems with pile
integrity, integrity testing of more than 20% of production piles may be required. A typical
reasonable approach for load-bearing piles is to subject the first 10 to 15 piles to be constructed
on a project to integrity tests to establish that the contractor’s construction practice at the site is
adequate. Thereafter, the frequency of such tests can be set to meet the specified frequency
criteria, can be reduced, or even perhaps eliminate further integrity tests if the construction
records for the remaining production piles are similar to those of the initial piles that were
subjected to integrity tests.[/highlight]