FPS Establishes Working Group to Investigate New Methods of Pile Integrity Testing

In 1997 CIRIA launched their Integrity testing in piling practice (R144), which formed the primary guide on this topic for the industry.   For sometime now there has been concern that even if 100% of working piles are subjected to integrity testing it is unlikely that test results will be a 100% reliable.  Furthermore technology has advanced considerably since 1997 and new techniques continue to be developed. 

Factors that can influence the reliability of the integrity testing conclusions*

  • As-built dimensions of the given pile and suitable pile head preparation for testing
  • easy access to the pile head the tester and his equipment • ability of a specific type of integrity test to detect various types piling fault
  • tester experience with a given integrity test under similar operating conditions
  • volume and quality of supplementary construction and site data used to interpret the results
  • level of knowledge and experience in signal interpretation • ability to determine the engineering significance of features in the test results
  • the basis on which threshold values (beyond which a pile is classified defective) are determined
  • reliability of automated algorithm for detecting whether the threshold has been breached

*taken from Cameron G and Chapman T, Quality assurance of bored pile foundations, Ground Engineering February 2004 p35 -40 

As a result the Federation of Piling Specialists (FPS) has established a Working Group to evaluate the many new methods of indirect pile testing, to address concerns that exist over their interpretation and ensure results are both robust and calibrated against each other and against existing direct testing methods.

With the development of a number of new methods for the integrity testing of large diameter and deep bored piles, such as Thermal Integrity Profiling (TIP testing) and optical methods, the FPS feels methods need further examination to ensure the data they provide is of practical significance before they become a mainstream choice for specifiers. Presently there is caution that the indirect nature of these new testing methods require ‘calibration’ against previous forms of testing to satisfy specifiers that the testing is reliable, and will provide the same or better ‘visibility’ of a constructed pile and its properties.

Additionally, Sonic Logging, an indirect testing method already well-established, will be examined further with a view to looking at ways of improving safety reducing safety-related issues typically arising during the placement of long telescopic logging tubes in deep bores.

Alasdair Henderson, Chair of the FPS, said: “These new indirect testing methods should be perfect for installation verification of large bored piles used in the foundations of heavy structures and in retaining walls; however it is critical that the data these new testing methods present is reliable and meaningful compared to existing testing methodologies. The primary task of the Working Group will be the ‘calibration’ of these new methods of testing against each other and existing pile integrity test methods so that reliable and meaningful data sets can be produced that not only endure scrutiny, but help promote these new methods to commonplace application.”