V – Defect That Is Not an Anomaly: A defect that is not an anomaly (i.e., a false negative) represents all the true defects that go undetected, such as: • “Soft bottom” conditions that were undetected by either the low strain impact method or thermal imaging. • Deviation from the vertical, which is not detected unless tested using a dedicated system. • Large bulges, which are undetectable by CSL testing. However, defects such as the ones listed above could have been detected by selecting a proper test method. Fig 5 - A small flaw Fortunately, such a small flaw affects neither the capacity nor the durability of the foun- dation element; thus, the flaw is not a defect IV - Anomaly That Is a Defect: An a maximum of about 330 , an increase of about 74%. The attenuation increased by 16 dB, which was an 84% decrease in the energy (Fig 6). Since this feature was quite shallow and the groundwater level much deeper than the location of the example of when an anomaly is actually a defect (i.e., true positive) is discussed hereafter. From the results of CSL testing performed on a drilled shaft, a major anomaly was discovered at a depths between 1.8 m and 3 m (6 ft and 10 ft), where the FAT increased from 190 μsec μsec to anomaly, it was decided to excavate around the pile to expose the anomaly. Upon excavating around the pile, visual obser- vations confirmed the test results and suspicions that this anomaly was indeed a flaw. Due to its size and location, the flaw was justly classified as a defect (Fig 7). DFI White Paper A team of experts was formed from the DFI Testing and Evaluation Committee and was chaired by Anna Sellountou, Ph.D., P.E., of Pile Dynamics, Inc. (PDI), to develop guidance on evaluating and interpreting the results of CSL testing. Recently, the team completed the white paper titled, "Terminology and Evaluation Criteria of Crosshole Sonic Logging (CSL) as applied to Deep Foundations." Based on an extensive literature survey and on the experience of the team members, the document essentially adopts the defini- tions presented above, defines three levels of anomalies and recommends the actions to be takes in each case in an attempt to resolve the anomaly. The white paper is currently under review and should be available through DFI later this year. Joram M. Amir, Ph.D., C.E., D.GE., is a Licensed Engineer No. 147 (Geotechnics and Structures) in Israel. With close to 60 years of experience as a geotechnical consultant, he also serves as the chairman of Piletest.com Ltd., developing innovative systems for pile integrity testing. Fig 6 - Ultrasonic test results on a drilled shaft Fig 7 - A defect in a drilled shaft DEEP FOUNDATIONS • MAY/JUNE 2019 • 95
