Abstract:
Large diameter, permanently cased drilled shafts have become an attractive and economical foundation type for major river bridges. However, with this type of foundation, concrete integrity anomalies are often encountered during post-construction, non-destructive testing above the mudline, where river water flows around the shaft. Thermal integrity profiling (TIP) results can be affected by the dynamic thermal environment of the flowing water above the mudline. Effects of the flowing water can also influence crosshole sonic logging (CSL) results in the form of exacerbated tube debonding and possibly concrete bleed. Further investigation by concrete coring occasionally finds bleed water channels. In most cases, these types of concrete integrity anomalies are not indicative of a flawed or a defective shaft. Examples of concrete integrity anomalies observed in river shafts above the mudline in TIP, CSL, and coring from recent projects in the South Central United States and New Jersey are presented, including discussion on the causal mechanisms. Recommendations on how to limit the potential for these types of anomalies and suggestions for further research will be presented.