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How accurate is PET for pile testing?

Updated: Jun 21, 2023

This is a question our users are often asked, so here are the facts:

PET (Pile Echo Tester) system for pile integrity test is used for two purposes:

  1. To check if the pile has any flaws

  2. To measure the length (depth) of the pile.

According to the pile integrity testing standard ASTM D5882, the first item is a question of interpretation, while the second one mainly depends on the selected wave speed. The PET software includes a wave speed calculator that suggests the wave speed for any combination of concrete quality and age. In most cases, this value lies between 3,600 and 4,400 m/s, so if you have no further information, go for 4,000 m/s. In most cases, this will ensure an accuracy better than 10%. This can be improved if you are testing a site with proper supervision and are given an as-made list of pile lengths. You can then establish the correct wave speed for this site and reduce the error to 5% or better.

Having obtained the correct wave speed, how accurate is the PET itself? We used the 11th Stress Wave Conference in Rotterdam last September (2022) to answer this question to conduct the first-ever ILS (Interlaboratory Study standard ASTM E691-22). Eight testers from Israel, The Netherlands, Spain, Poland, and Malaysia (most of them using PET) tested nine precast piles. Before driving, we measured their lengths which were between 8 and 17 m, as well as each one’s wave speed. This information was not disclosed to the participants.

The results: When the test reports were adjusted to the true wave speed, the PET achieved an accuracy better than 2%. For a normal distribution, 95% of the results lie between 4% of the mean. - constantly innovating!

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