Modeling Inclusions in Deep Foundations Integrity Tested by Thermal Methods-Paper

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The study uses COMSOL Multiphysics to model heat generation and transfer in a 1.5 m diameter, 10 m long drilled shaft, assessing how construction defects affect thermal integrity measurements. The model simulates concrete hydration and heat dissipation into surrounding saturated sand, with temperatures recorded at five locations around the reinforcement cage.<br /><br />Three anomaly types were examined: full-cross-section soil layers, loss of concrete cover exposing reinforcement, and spherical soil inclusions extending inward from the shaft edge. Larger defects produced stronger and broader temperature reductions. Thin full-section layers and defects affecting less than about 5% of the cross section generated weak signals and were more difficult to detect. The number and location of affected measurement wires helped distinguish the size and position of localized inclusions. The modeled results also suggest that some anomalies—particularly small cover losses—may be detectable thermally even when other integrity methods are unlikely to identify them.<br /><br />The researchers compared simulations with field data from a shaft containing intentional tremie-related defects. The modeled temperature patterns broadly matched measured profiles and corroborating core results, though the model produced sharper transitions than observed. Differences may reflect the simplified defect geometry and unmodeled cage eccentricity.<br /><br />Overall, numerical modeling can help evaluate thermal testing’s detection limits and interpret anomalies alongside construction records and other inspection methods. However, the results depend on assumed concrete, soil, geometry, and environmental properties. The study concludes that very small cross-sectional reductions and layers thinner than roughly 50 mm may produce faint thermal signatures, underscoring the need for engineering judgment when setting acceptance criteria.

Keywords

COMSOL Multiphysics

thermal integrity testing

drilled shaft

heat transfer

concrete hydration

construction defects

soil inclusions

reinforcement cage

temperature measurements

numerical modeling