Single-Tube Ultrasonic Testing of Pile Integrity

It is now universally acknowledged that in bored piles (drilled shafts, caissons) flaws can, and therefore will, occur. The majority of the important flaws can be detected by standard non-destructive testing methods. There are situations, however, when none of these methods is viable. One example is that of small diameter piles, penetrating through rockfill with large cavities and then socketed into rock. The Israel Ministry of Construction and Housing initiated a research project to evaluate the applicability of single hole ultrasonic testing (SHUT) to such piles. The following parameters were to be investigated: Minimum age of concrete that enables testing, the most suitable tube material, tube diameter and most advantageous probe spacing. The goal of this work was to establish the performance envelope of the method and propose a suitable specification for the test procedure. A suitable test site was selected in Ma'ale Modi'in, Israel, where the subsoil consists of weathered hard dolomite with hard clay pockets. Altogether ten piles were tested, of which eight contained known defects. All testing was performed using the CHUM system manufactured by Piletest.com Ltd. The results prove that SHUT is a very suitable means for integrity testing of small-diameter piles, and may also serve as a clean alternative to radioactive testing of large-diameter piles.