Crosshole Sonic Logging Anomalies in Large Diameter Bored Piles Constructed Under Polymer Support Fluid: Investigation and Assessment

Post-construction integrity testing is a critical part of the quality assurance process for cast-in-place concrete bored piles. Crosshole sonic logging (CSL) is a common integrity testing method that is used for this purpose. This paper describes anomalies identified by CSL in multiple large diameter bored piles constructed using tremie concrete placed under polymer support fluid in London, United Kingdom. In response to the CSL results, further investigation using tomography and test coring was carried out and is described, along with the design analyses completed to assess the impact of the anomalies on pile capacity. Possible causes for the anomalies are identified and some of the implications for design and construction of tremie concrete bored piles under polymer support fluid are discussed. Recommendations are made regarding a project design and construction team’s response to anomalies identified by integrity testing.