However, the test has certain limitations:
• This method is expensive and requires drilling boreholes
parallel to existing piles.
• Parallel seismic testing is commonly used for estimation
of pile length, not pile integrity. The stress wave generated
by hammer impact travels through the pile and surrounding
soil. The soil profile may significantly affect stress
waves, resulting in a poor or misleading signal for
data interpretation.
• Accurate data interpretation requires knowledge about
soil profile.
• The borehole should be longer than pile length. This
makes drilling challenging when there is no knowledge
about the pile length.
Concluding remarks
Alternative methods, such as removing soil, extracting core
samples and visual examination are generally expensive,
provide little information about other locations and create
significant delays in the decision-making process and/or in
the construction timeline. In addition, intrusive methods
such as extracting cores might negatively impact the safety
and reliability of an existing pile.
Non-destructive testing has widely been used for quality
control of deep foundations in new construction, as well
as forensic evaluation and condition assessment of existing
piles. NDT methods provide cost-effective and easy
to deploy tools for the evaluation of integrity in piles and
deep foundations.
Some codes and guidelines strongly recommend performing
integrity tests of deep foundations either for new construction
or for comprehensive evaluation of existing structures.
Some other codes and guidelines consider integrity testing
as an optional quality control test. However, these codes and
guidelines authorize engineers and designers to increase the
superstructure loads should the integrity of piles have been
verified through NDT methods.
Low strain pile integrity testing, ultrasonic crosshole
testing, thermal integrity profiling and parallel seismic
testing are widely used for quality control of new construction
and integrity assessment of existing deep foundations.
Among these methods, PIT is very cost-effective, fast and easy
to implement for both new construction and existing structures.
It is recommended to evaluate integrity initially by the
PIT method, then proceed to use advanced non-destructive
integrity testing methods if PIT results are not conclusive or
PIT shows an integrity issue. Application of the PIT method
for existing structures is more complicated because access to
pile heads is often limited due to the presence of superstructures
or pile caps.
Moreover, it is recommended that non-destructive
integrity testing be performed by a trained technician in
order to collect reliable data during field work. Interpretation
of integrity test data requires basic knowledge on the concept
of non-destructive integrity testing. Complementary information
(i.e. knowledge of the construction record, design
documents, soil profile, concrete mix design, compressive
strength) help to interpret field data and analyze test results
more accurately.
References
1. ACI Committee 228. “Report on Non-destructive Test
Methods for Evaluation of Concrete in Structures”. ACI
228R-13, 84p.
2. AMIR, J., “Single-tube ultrasonic testing of Pile Integrity,
Proc. of the International Deep Foundations Congress, 2002,
ASCE Geo-Institute.
3. AMIR, E., ET AL., “Inferring pile shape from pulse-echo
test records by evolutionary algorithm”. 9th International
Conference on Testing and Design Methods for Deep
Foundations, Kanazawa (Japan), 2012.
4. ASTM D4945-17, Standard Test Method for High-Strain
Dynamic Testing of Deep Foundations, ASTM International,
West Conshohocken, PA, 2017, www.astm.org
5. ASTM D5882-16, Standard Test Method for Low Strain
Impact Integrity Testing of Deep Foundations, ASTM
International, West Conshohocken, PA, 2016, www.astm.org
6. ASTM D6760-16, Standard Test Method for Integrity Testing
of Concrete Deep Foundations by Ultrasonic Crosshole
Testing, ASTM International, West Conshohocken, PA, 2016,
www.astm.org
7. ASTM D7949-14, Standard Test Methods for Thermal
Integrity Profiling of Concrete Deep Foundations, ASTM
International, West Conshohocken, PA, 2014, www.astm.org
8. BAKER ET AL., “Use of nondestructive testing to evaluate
defects in drilled shafts: Results FHWA research, TRB, 1991.
9. BRIAUD, J. ET AL., “Defect and length predictions by NDT
methods for nine bored piles”, Proc. of the International
Deep Foundations Congress 2002, ASCE Geo-Institute.
10. CIRIA Report 144, “Integrity testing in piling practice”, 1997.
11. COE, J.T., ET AL., “Application of Non-Destructive Testing
to Evaluate Unknown Foundations for Pennsylvania
Bridges”. Final Report for Pennsylvania Department of
Transportation, Temple University, 2013, 270 p.
12. DAVIS, A., “The Development of non-destructive smallstrain
methods for testing deep foundations. A Review.”,
TRB, 1991.
13. DEEP FOUNDATIONS INSTITUTE. “Manual for Non
Destructive Testing and Evaluation of Drilled Shafts”. USA,
2005.
14. MASSOUSI, N., ET AL., “Non-Destructive Testing of Piles
Using the Low Strain Integrity Method”. Fifth International
Conference of Case Histories in Geotechnical Engineering,
Paper No. 9.03, New York, NY, April 13-17, 2004.
15. MULLINS, G., ET AL., “Thermal Integrity of Drilled Shaft –
Final Report”. Technical Report for Florida Department of
Transportation, University of South Florida, May 2007, 214 p.
16. RAUSCHE, F.A., “A comparison of Pulse Echo and Transient
Response Pile Integrity Test Methods”, TRB, 1991.
17. RAUSCHE, F.A., ET AL., “Pile integrity testing and analysis”.
Proceedings of the Fourth International Conference on the
Application of Stress-Wave Theory to Piles. The Hague, 1992
18. SAINT-PIERRE, F., ET AL., “Concrete Quality Designation
based on Ultrasonic Pulse Velocity”. 2016, Construction and
Building Materials, Vol. 125, 1022-1027.
FEATURE
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