Timber piles are widely used for supporting marine structures. As they age, it becomes critical that their condition be assessed so that their remaining useful life and service potential be determined. Visual inspection is the most commonly employed non-destructive testing (NDT) procedure due to its simplicity, ease of execution, and cost-effectiveness. However, the inspection is limited to the surface of the pile and assessors may misinterpret their observations. Sounding is a straightforward technique for testing timber piles above water, providing an initial indication of deterioration. However, it requires follow-up with more precise assessment methods. Timber pile coring tests, while valuable for evaluating pile integrity and strength, have drawbacks such as potential damage to the pile, limited representation of the entire cross-section, and reliance on technical expertise. Ultrasonic testing has been developed to evaluate the soundness of timber structures. However, small holes caused by marine borers may lead to misinterpretation of the data and the material characteristics of timber may cause further evaluation challenges.
In this study a wooden pole assessment technology used by telecommunication and power transmission companies for over 20 years was successfully adapted for underwater use to determine the extent of internal decay pockets in timber piles. The ROVing Intelligence T7 underwater inspection Remotely Operated Vehicle (ROV) employed this proven NDT approach by drilling a fine (1.5mm) needle into the timber pile at a constant speed and measured the resistance to drilling to determine any internal decay. An extremely accurate picture of the condition of the timber pile was produced, returning good/bad results for:
The inspection procedure minimised damage to the pile structure as there was a reduction in the need to drill larger inspection holes and the real-time resistance analysis allowed the engineer to employ a very targeted and efficient assessment regime.
It has been concluded that a standardised, repeatable, non-destructive and auditable timber pile assessment method can be confidently used to understand condition, providing the evidence to inform and influence a prioritised plan for timber pile renewals.