New Insights on Detecting Flaws with CSL and TIP-Paper

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The paper synthesizes research on crosshole sonic logging (CSL) and thermal integrity profiling (TIP) for detecting flaws in drilled-shaft concrete, including studies with intentional defects and production shafts with soft-bottom conditions.<br /><br />The methods are complementary. CSL is generally effective for flaws within the reinforcing cage, soft bottoms, and tremie breaches, but may miss weak concrete and flaws outside the cage. TIP can readily identify weak concrete and flaws outside the cage, but inclusions inside the cage are difficult to detect; soft bottoms and tremie breaches may be detectable. Neither method alone provides a fully reliable assessment, and detection depends on factors beyond flaw size, including location, material contrast, shaft geometry, and interpretation.<br /><br />The research highlights two improvements to interpretation. CSL assessments should consider both arrival-time delay and relative energy loss, since some flaws affect one measure more strongly than the other. TIP results should be evaluated over time, not only by depth: flaw-related temperature differences and delayed hydration can be clearest before peak temperature and may fade by the peak. Temperature-versus-time plots can also help distinguish soft-bottom conditions from normal temperature decline at the shaft base.<br /><br />The authors recommend selecting CSL, TIP, or both according to project-specific risks and maintaining thorough construction records. CSL should be interpreted using the Deep Foundations Institute’s recommended protocol. TIP evaluation should combine temperature-versus-depth profiles, effective-radius results, other integrity tests, construction information, and temperature-versus-time plots comparing suspected flaw zones with nearby baseline measurements. Because time-series data are essential, the authors recommend wire-based TIP rather than probe-based testing.

Keywords

crosshole sonic logging

thermal integrity profiling

drilled-shaft concrete

construction defects

soft-bottom conditions

tremie breaches

reinforcing cage

flaw detection

temperature-time plots

deep foundations institute