Analyzing Thermal Integrity Profiling Data for Drilled Shaft Evaluation-Article

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Thermal integrity profiling (TIP) evaluates drilled shafts by measuring heat generated during concrete hydration. Unlike methods that rely on access tubes, TIP can identify anomalies across the full shaft cross-section and indicate reinforcement-cage alignment. Temperature profiles generally reflect shaft shape, but interpretation is complicated near shaft ends, where heat escapes vertically, and at changes in surrounding conditions, such as transitions between soil, water, or air.

This paper examines hyperbolic temperature corrections for these end effects and mid-shaft thermal transitions. After correcting measured temperatures, analysts can apply a temperature–radius (T–R) relationship to estimate the shaft’s effective radius—the radius of sound concrete that would produce the observed temperature. The author first analyzed modeled data, then applied the approach to field measurements from a partially cased shaft.

Modeling and field results showed that hyperbolic curves can represent temperature changes near the top and bottom of a shaft and at boundary transitions. The correction parameter <em>a</em>, which describes the distance over which a transition affects temperatures, increased approximately linearly with the square root of curing time. Top-end behavior was also influenced by changing air temperatures. Analyses at different concrete ages produced similar effective-radius profiles, suggesting that the method is relatively insensitive to testing time during the main hydration period.

The field results were consistent with construction records: the upper shaft matched the casing radius, while the uncased lower section was slightly larger than intended. The author cautions that mid-shaft corrections should only be applied when site evidence supports a genuine change in boundary conditions, since actual changes in shaft radius can produce similar temperature patterns. Parameter choices must also remain physically plausible; seemingly good curve fits alone are not sufficient.

Keywords

thermal integrity profiling

drilled shafts

concrete hydration

temperature correction

hyperbolic curves

effective radius

end effects

boundary transitions

field measurements

shaft anomalies