Drilled Shaft Acceptance Criteria Based upon Thermal Integrity Profiling-Paper

Paper

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The paper presents Thermal Integrity Profiling (TIP) as a non-destructive method for assessing drilled-shaft quality, particularly for shafts cast under slurry where direct inspection is difficult. TIP measures heat generated during concrete hydration using embedded thermal cables or probes in access tubes. Temperature patterns along the shaft are used, together with concrete-volume records, to estimate effective shaft radius and identify defects, concrete-cover loss, and reinforcing-cage misalignment. Unlike many other testing methods, TIP can assess the full cross-section, including concrete outside the reinforcing cage.<br /><br />The authors propose acceptance criteria based on both radius reduction and minimum concrete cover. Shafts with 0–6% radius reduction and adequate local cover are classified as satisfactory. A reduction greater than 6% or failure to meet cover requirements triggers further evaluation, including structural review and consideration of construction records and soil conditions. TIP results are time-sensitive and require measurements during the hydration process, as well as embedded cables or access tubes.<br /><br />A Washington State case history illustrates the method: a 10-foot-diameter, 125-foot-long shaft showed an anomaly at about 90 feet, with a 14.2% radius reduction and insufficient cover. Coring confirmed the defect, which was pressure-grouted. The paper concludes that TIP can identify defects early and provide information useful for consistent, risk-informed shaft acceptance.

Keywords

Thermal Integrity Profiling

TIP

drilled-shaft quality

non-destructive testing

concrete hydration

effective shaft radius

radius reduction

concrete cover

defect detection

reinforcing-cage misalignment