PROJECT CONTEXT

This study focused on the reliability of Pile Integrity Testing (PIT) for assessing the structural integrity of cast-in-place concrete piles.

→ The objective was to evaluate how different types of defects influence the measured signal and whether PIT alone can provide a reliable assessment.

ENGINEERING CHALLENGE

The key challenge was the uncertainty in interpreting PIT results when defects are present.

In practice, this creates two critical risks:

• defective piles being classified as acceptable,
• sound piles being rejected due to misleading signals.

→ Both scenarios have direct financial and safety implications.

LIMITATIONS OF THE STANDARD APPROACH

The standard PIT procedure relies on:

• wave reflection analysis,
• visual interpretation of signal anomalies.

However, the method has inherent limitations:

• signal response depends on multiple interacting factors:
  • defect geometry,
  • depth of the defect,
  • impedance contrast.

→ As a result, different defects can produce very similar signals.

ADVANCED METHODOLOGY – NUMERICAL SIMULATION

To better understand these limitations, a Finite Element Method (FEM)-based numerical simulation was performed. The analysis included:

• multiple defect scenarios (necking, inclusions, cross-section changes),
• variation in defect size and depth,
• simulation of wave propagation and reflections along the pile,
• Hilber–Hughes–Taylor numerical integration method.

→ This approach enabled controlled evaluation of cause–effect relationships between defects and signal response.

Reflectogram surface – Asymmetric reduction of the cross-sectional area at two locations along the pile.

KEY ENGINEERING INSIGHT

The simulation demonstrated that:

• similar signals can originate from fundamentally different defects,
• certain defects may produce weak or undetectable reflections,
• signal interpretation without additional analysis can be misleading.

→ There is no unique relationship between a defect and the resulting PIT signal.

RESULTS AND PRACTICAL IMPACT

Key outcomes:

• improved reliability in interpreting field test results,
• identification of scenarios where PIT alone is insufficient,
• better decision-making regarding the need for additional testing methods (e.g., CSL, PDA).

Practical impact:

• reduced risk of incorrect acceptance or rejection of piles,
• more efficient quality control strategy,
• increased confidence in foundation performance.

→ The study provided a more realistic understanding of PIT capabilities and limitations.

STRATEGIC CONCLUSION

This case study highlights that:

• advanced analysis, such as numerical simulation,
• is essential for bridging the gap between measured signals and actual pile condition.

→ PIT is not a standalone decision tool — it is an interpretation-dependent method.

Cosic M., Folic B., Folic R.: Numerical Simulation of the Pile Integrity Test on Defected Piles, Acta Geotechnica Slovenica, Vol. 11, No. 2, 2014. pp. 5-19.