Field and Finite Element Based Parameter Studies on the Sensitivity of Thermal Intergity Testing of Drilled Sshafts-PPT Presentation

PPT Presentation

Pdf Summary

The study evaluates Thermal Integrity Profiling (TIP) for detecting anomalies in cast-in-place drilled shafts, comparing field observations with time-dependent two-dimensional finite-element analyses. TIP uses cables installed with the reinforcement cage and, unlike Cross-Hole Sonic Logging (CSL), assesses the concrete cover zone without requiring access pipes.<br /><br />At the Testfeld Lehmen site in Germany, a test shaft was constructed with four deliberately introduced soil inclusions and instrumented for both TIP and CSL. CSL clearly detected several inclusions. TIP measurements showed temperature differences associated with inclusions and a section with documented concrete overconsumption, illustrating the value of combining the methods.<br /><br />The finite-element study examined the effects of shaft diameter, concrete heat generation, segregation, soil thermal properties, anomaly size, sensor spacing, staged placement, and evaluation time. Results show that TIP readings are strongly influenced by these factors. Large anomalies produce detectable temperature differences, and significant results generally occur during the first hours after casting, when hydration heat is greatest. In the modeled cases, anomalies around 300 × 300 mm or larger could be detected at a temperature-difference threshold of about 6%; large anomalies could remain detectable beyond the time of peak temperature. A typical 30 cm sensor spacing could identify large anomalies.<br /><br />The authors conclude that TIP is a practical, reliable method that does not interfere with concrete placement. However, interpretation requires care: thermal anomalies depend not only on defects but also on concrete and ground properties and construction conditions. Detailed engineering assessment should therefore consider all relevant thermal inputs and temperature measurements over time, particularly when results inform structural analysis. The findings are intended to support future updates to piling integrity-testing recommendations.

Keywords

Thermal Integrity Profiling

TIP

cast-in-place drilled shafts

anomaly detection

finite-element analysis

concrete inclusions

Cross-Hole Sonic Logging

hydration heat

piling integrity testing

soil thermal properties