Foundation Testing Services specialise in validating the integrity of various foundation systems. Integrity testing is undertaken to verify that the uniformity of concrete structures is consistent and free from problematic physical defects such as cracks and voids. The test can also determine the pile length and consistency of the cross-sectional area, therefore, indicating if the piles have been installed to the desired depth and correct diameter. This process is undertaken prior to the development of the superstructure and is non-destructive.

 

Perhaps the most common form of integrity test is carried out on piled foundations. The installation of sound piles can be a complex task due to the physical properties of concrete and ground conditions. Challenges may arise during the formation of piles that can result in structural anomalies. The result? A pile that most likely will not facilitate a bearing capacity to support the specified loadings.

 

The above issues cannot be solved if they are not initially discovered, and that is where Foundation Testing Services come in. Below is a summary of the methodology employed in integrity testing.

 

• The Transient Dynamic Response (TDR) test is a rapid method of assessing the integrity of both pre-cast and cast-in-situ concrete piles.

 

• After ensuring that the concrete in the pile head is visually free of loose materials and contaminants, a geophone sensor is placed in contact with the pile head and struck axially using the systems force response hammer.

 

 

• ​The response of both transducers is measured simultaneously, and the velocity and force signals are processed and displayed on the test unit. 

 

• By using a known wave velocity, it is possible to calculate the pile length. Reflections can also be obtained from acoustic anomalies within the pile shaft. At low frequencies, the response is generally linear allowing measurement of the dynamic pile head stiffness.

 

 

• Oscillation of the pile head enables an acoustical survey of the pile, which can identify potential discontinuities such as cracks, voids, and changes in cross-sectional area. A secondary feature of the test provides identification of the pile-toe.

 

• On-site analysis of the received signal can identify at what point along the pile shaft the potential discontinuity occurs. An instant assessment of each pile tested can therefore be achieved. Where possible rectification of any anomaly can be carried out before subsequent retests are applied.

 

Following the physical testing of the pile, a full report is dispatched and contains a copy of the signals obtained from each pile and an indication of the pile toe seat reflection figure. The test results are interpreted in such a way as to make the signal change point apparent and the approximate pile length calculated.