Once a pile is cast, it's buried out of sight. Low-strain integrity testing offers a fast, non-destructive way to check that each pile has been formed as intended, before the structure goes on top.

How it works

A sensor is attached to the top of the pile and the pile head is tapped with a small hand-held hammer. This sends a stress wave down the pile. When the wave meets a change, such as the pile toe, a change in cross-section or a defect, part of it is reflected back up and recorded. The results show the pile's condition along its length and give an estimate of its overall length.

What it can find

Low-strain testing can identify:

• Necking or reductions in cross-section
• Bulges and increases in section
• Voids, cracks and soil inclusions
• Areas of poor concrete
• Piles shorter than expected

What it can't do

It doesn't measure load capacity, which requires load testing. Very small defects may not show up, and results become less reliable in very long, slender piles or where one defect masks others further down.

Getting accurate results

Pile heads should be cut down to sound concrete, clean, level and accessible, and the concrete needs time to gain strength before testing, usually around a week after casting. Many piles can be tested in a day, making it ideal for checking a whole site quickly rather than a few samples.

Pile integrity testing in London and across the UK

ACUO Structural Insights provides low-strain pile integrity testing in line with the principles of ASTM D5882 and ICE SPERW, for piling contractors, main contractors and engineers across London, Kent, Essex and the South East.

For full details on what the service covers, visit our pile integrity testing service page. Where ground conditions are also a concern, our void detection service can identify subsurface voids and poor compaction around pile heads.

Need piles tested? Call 07340 549892 or email [email protected].