Discover unwanted anomalies with Specialised Pile Integrity Testing

Once an anomaly is identified in the interpretation of the results, further appropriate testing may be carried out. Where practical the pile is exposed at the approximate depth of the anomaly to confirm the findings of the integrity test.

Recently Geosure using the DIAGNOSTIC PILE ANALYSER identified acoustic anomalies in several piles. On an upmarket development in Durban, Geosure were appointed to carry out integrity tests on all piles cast. 25% of the piles tested showed severe necking in the pile’s shaft. These piles were exposed to the depths where acoustic anomalies were identified. The adjacent plates show the severity of some of the anomalies identified.

Pile integrity testing is carried out by Geosure (Pty) Ltd using the Diagnostic Pile Analyser supplied by NDT Technology and Piletest.com, which provides a rapid and relatively inexpensive means of screening groups of piles for anomalies, which might affect pile performance. These tests can be usefully implemented on all types of individual cast in-situ piles. Only limited information may be obtained for secant type piling because of binding between adjacent piles. Precast piles may be checked for mechanical damaged cracks. A pile integrity assessment can only be as good as the quality of the test data. The DIAGNOSTIC PILE ANALYSER is a purpose built system which makes extensive use of the latest digital signal acquisition and data processing techniques to ensure the integrity and quality of the test data. The Analyser has provision to carry out both Frequency and Sonic Echo test methods on each pile. The combination of these methods aids the interpretation of complex results and enables difficult assessments to be made with greater confidence and reliability.

Pile Echo Tester (PET) is a user friendly, highly flexible solution for the testing a large number of deep foundations quickly and accurately. As seen below are the PET equipment. PET is a modular, computer independent system that attaches itself to the USB of regular notebook, tablet PC or Pocket PC via Bluetooth protocol.

Some of the larger projects on which Geosure have carried out pile Integrity testing are:

The structural defects in the piles shown in the accompanying photographs were confirmed when exposed by excavation around the pile shafts after anomalies were identified in the integrity test results.

Testing is carried out regularly for the following contractors:

Over the past 20 years Geosure have invested substantial time and effort in developing pile integrity testing skills in South Africa. With the support of NDT Technology in the UK, local personnel have been trained abroad to operate the equipment and evaluate test results. The stature of testing together with the level of skill and experience achieved has established Geosure firmly as the leaders in this field in Southern Africa.

At present it is acknowledged that in South Africa, Geosure has developed and pioneered integrity testing to the point where most piling contractors and many consultants accept the test results with confidence.

The integrity testing service offered by Geosure is considered by many contractors and clients in the marketplace to add significant value to piling contracts, particularly as such testing provides a rapid and relatively inexpensive means of screening the structural integrity of all piles on a site, as opposed to testing a select few piles using pile load tests.
Where acoustic anomalies are identified in test results, further investigation of the piles in question may be required.

Sonic Logging provides a method of assessing the homogeneity of concrete in piles or other mass foundation, such as diaphragm walls. Sonic logging has no inherent limitations on penetration depth of the size or shape of structure, which can be tested. No direct access is required to the concrete surface and the method can be used to test structures with low cut off levels at an early stage. Access tubes have to be cast into the structures to facilitate the tests and pre-selection of units to be tested is therefore necessary.

The tests are directed towards anomalies identified within a group of results, which may warrant further investigation.
For the ultrasonic test at least two tubes, either plastic or steel of minimum diameter 50mm, are cast in the pile (steel tubes are preferable as these are more durable, are less likely to be damaged and less prone to debonding with the concrete). The tubes must be completely filled with water to act as an acoustic coupling agent between the probes and the tube wall. A transmitter of ultrasonic pulses is lowered in one of those tubes and a receiver in another until they reach the base of the pile. Both the transmitter and receiver probes are connected to the CHUM software (a ruggedized pen computer), which records the first arrival time (FAT) and the energy attenuation as the probes are simultaneously raised to the top. As long as the FAT and the energy attenuation are relatively constant, one may deduce that the concrete quality is also uniform and the pile is therefore acceptable.

On the other hand, if at some level there is a noticeable increase in the FAT and / or in the energy attenuation, it means that the concrete at this level is inferior or defective. In such a case, the test may be repeated with the transmitter and receiver at different levels, a technique that enables the determination of both location and extent of the defect (tomography). Consistent transmission characteristics indicate anomalous zones within the sonic transmission profile are immediately obvious and are noted. 

Installing an increased number of tubes on the perimeter gives an almost complete coverage of the pile cross-section. This method of testing is especially suitable for testing large diameter piles. The piles can be tested after the concrete has gained some strength, usually at an age of seven days or more from casting.