Situation
Communications towers are extremely important, especially in remote areas and, due to their location, they are very expensive to maintain or replace. With no construction records available, our client needed to have a good understanding of the condition of the concrete pile of the tower in order to estimate its lifespan.
A pile integrity survey would allow them to investigate if an immediate intervention would be needed on the communication towers, or if they were able to continue in service.
Solution
Pile integrity testing is based on sonic echo principles, where an impact is applied on the top of the pile and the reflected echoes are recorded after each individual impact. The wave propagation and reflection is generally based on the same principles as of GPR, but with a lot slower speed.
Pile integrity can provide information about: the continuity of the pile, defects, such as cracks, necking or bulging. It can evaluate unknown length of piles or shafts. Although it has important limitations to account for (e.g. can’t be used over pile caps, it doesn’t provide information about bearing capacity, not effective in evaluating sections of pile below cracks that crosses the entire cross section of the pile) it is an excellent methodology for a quick evaluation of a pile. The results usually indicating major defect or the depth of the toe of the pile.
The pile integrity test for the project was carried out as per ASTM D 5882 standard. It governs how the data collection should be carried out and what measures must be taken to get accurate results. The data analysis was done using a signal analysis software package.
Due to the short length of the pile and the limitations of the equipment, the results showed some uncertainty, but overall it seemed the pile is in good condition.
As an addition, a couple of circumferential GPR lines were collected to investigate the rebar pattern of the pile. The results indicated four vertical rebar at various depths.
